Endothelin-1 inhibits PAF-induced paw oedema and pleurisy in the mouse

Evaluation of anti-inflammatory activity and molecular docking study of new aza-bicyclic isoxazoline acylhydrazone derivatives

The aim of this study was to investigate the anti-inflammatory effects of two new isoxazoline-acylhydrazone derivatives: N'-(4-methoxybenzylidene)-6-(4-nitro-benzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-123) and N'-(4-chlorobenzylidene)-6-(4-chlorobenzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-99). An air pouch induced by carrageenan was used for screening the best dose of R-99 and R-123. Using this mouse model, leukocyte migration and cytokine levels (TNF-α and IL-1β) were determined. Paw edema induced by several phlogistic agents and vascular permeability induced by acetic acid were employed to investigate the mechanism of action of the isoxazoline-acylhydrazone derivatives. A docking study was performed with the human histamine H1 receptor to investigate potential antihistaminic activity. Treatment with the compounds reduced leukocyte migration in the air pouch at all doses tested. TNF-α and IL-1β levels were similarly reduced by the two compounds. Vasoactive amines were inhibited in models of paw edema induced by several agents and vascular permeability induced by acetic acid. The docking study suggests that R-99 and R-123 may be inhibitors of the histamine H1 receptor. In conclusion, the results indicate that R-99 and R-123 exhibit promising anti-inflammatory activity related to their ability to inhibit TNF-α, IL-1β, and vasoactive amine production, as well as reduce leukocyte migration and inhibit mast cell degranulation.

Further analysis of acute antinociceptive and anti-inflammatory actions of 4-phenylselenyl-7-chloroquinoline in mice

A new quinoline containing selenium, 4-phenylselenyl-7-chloroquinoline (4-PSQ), was described and synthetized by our research group. Recently, we demonstrated the potential antinociceptive and anti-inflammatory of 4-PSQ. For this reason, the first objective of this study was to expand our previous findings by investigating the contribution of glutamatergic, serotonergic, and nitrergic systems to the acute antinociceptive action of this compound. Pretreatment with 4-PSQ (0.01-25 mg/kg, p.o.) reduced the nociception induced by glutamate. MK-801 (an uncompetitive antagonist of the N-Methyl-d-aspartate (NMDA) receptor) blocked the antinociceptive effect exerted by 4-PSQ (25 mg/kg, p.o.) in the acetic acid-induced abdominal writhing test. The pretreatment with WAY100635 (a selective antagonist of 5-HT_1A receptor), ketanserin (a selective antagonist of 5-HT_2A/2C receptor), and pindolol (a nonselective antagonist of 5-HT_1A/1B receptors) partially blocked the antinociceptive effect caused by 4-PSQ (25 mg/kg, per oral, p.o.) in the acetic acid-induced abdominal writhing test. Nitric oxide precursor, l-arginine hydrochloride, partially reversed antinociception caused by 4-PSQ or ω-nitro-l-arginine (l-NOARG). Treatments did not modify the locomotor and exploratory activities of mice. Additionally, the acute anti-inflammatory effect of 4-PSQ in a model of pleurisy induced by carrageenan in mice was investigated. 4-PSQ reduced the cellular migration, pleural exudate accumulation, and myeloperoxidase activity induced by carrageenan exposure. 4-PSQ protected against the increase in reactive species levels and reduction of nonprotein thiol levels induced by carrageenan. Data presented here showed that the modulation of serotonergic, nitrergic, and glutamatergic systems contributed to the antinociceptive effect of 4-PSQ and it reinforced the therapeutic potential of this quinolinic compound for acute inflammation.

A biotinylated peptide, BP21, as a novel potent anti-anaphylactic agent targeting platelet-activating factor

Platelet-activating factor (PAF) is an important mediator of anaphylaxis and is therefore an anti-anaphylactic drug target. We recently reported that synthetic N-terminally biotinylated peptides (BP4-BP29) inhibit PAF by directly interacting with PAF and its metabolite/precursor lyso-PAF. In this study, we investigated whether the biotinylated peptides can inhibit anaphylactic reactions in vivo. In mouse models of anaphylaxis, one of the peptides, BP21, markedly and dose-dependently inhibited hypothermia with a maximum dose-response within 30 min after administration, even at doses 20 times lesser than doses of the known PAF antagonist CV-3988. In contrast, the anti-hypothermic effect of BGP21, in which the Tyr-Lys-Asp-Gly sequence in BP21 was modified to a Gly-Gly-Gly-Gly sequence, was less than that of BP21. The alanine scanning and shuffling the amino acid residues of BP4 (Tyr-Lys-Asp-Gly) demonstrated that the Tyr-Lys-Asp-Gly consensus sequence is important for the inhibitory effect of the peptide on hypothermia. BP21 also suppressed vascular permeability during anaphylaxis with a maximum dose-response within 30 min of administration. In a rat model of hind paw oedema, BP21 significantly inhibited the oedema induced by PAF but not that induced by the other pro-inflammatory mediators, such as histamine, serotonin, and bradykinin. Tryptophan fluorescence measurements showed that BP21 interacted with PAF, but not with histamine, serotonin, or bradykinin. In contrast, BGP21 did not interact with PAF. These results suggest that biotinylated peptides, especially BP21, can specifically and markedly inhibit anaphylactic reactions in vivo and that this involves direct interaction of its Tyr-Lys-Asp-Gly region with PAF. Therefore, a biotinylated peptide, BP21, can be used as novel potential anti-anaphylactic drugs targeting PAF. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Angiotensin peptides attenuate platelet-activating factor-induced inflammatory activity in rats

Angiotensin (Ang)--a peptide that is part of the renin-angiotensin system-induces vasoconstriction and a subsequent increase in blood pressure; Ang peptides, especially AngII, can also act as potent pro-inflammatory mediators. Platelet-activating factor (PAF) is a potent phospholipid mediator that is implicated in many inflammatory diseases. In this study, we investigated the effects of Ang peptides (AngII, AngIII, and AngIV) on PAF-induced inflammatory activity. In experiments using a rat hind-paw oedema model, AngII markedly and dose-dependently attenuated the paw oedema induced by PAF. The inhibitory effects of AngIII and AngIV on PAF-induced paw oedema were lower than that of AngII. Two Ang receptors, the AT1 and AT2 receptors, did not affect the AngII-mediated attenuation of PAF-induced paw oedema. Moreover, intrinsic tyrosine fluorescence studies demonstrated that AngII, AngIII, and AngIV interact with PAF, and that their affinities were closely correlated with their inhibitory effects on PAF-induced rat paw oedema. Also, AngII interacted with metabolite/precursor of PAF (lyso-PAF), and an oxidized phospholipid, 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC), which bears a marked structural resemblance to PAF. Furthermore, POVPC dose-dependently inhibited AngII-mediated attenuation of PAF-induced paw oedema. These results suggest that Ang peptides can attenuate PAF-induced inflammatory activity through binding to PAF and lyso-PAF in rats. Therefore, Ang peptides may be closely involved in the regulation of many inflammatory diseases caused by PAF.

Biotinylated heptapeptides substituted with a D-amino acid as platelet-activating factor inhibitors

Platelet-activating factor (PAF), a potent lipid mediator, is implicated in many inflammatory diseases, and therefore may serve as a direct target for anti-inflammatory drugs. We previously reported that synthetic biotinylated peptides having a Tyr-Lys-Asp-Gly sequence markedly inhibit PAF-induced inflammation by direct binding, and that two synthetic fluorescence-labelled heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp and D-Lys-Trp-Tyr-Lys-Asp-Gly-Asp) with high stability in plasma specifically bind to PAF-like lipids (oxidized- and lyso-phosphatidylchoine). In this study, synthetic heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp) coupled to a biotin molecule through the N-terminal amino group and ε-amino group of N-terminus Lys, (Btn)KP6 and K(Btn)P6, respectively, and their biotinylated peptides substituted with D-Lys at the N-terminus, (Btn)dKP6 and dK(Btn)P6, respectively, were investigated for their effects on PAF-induced inflammation. In the experiments using a rat model of hind paw oedema, (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 significantly inhibited PAF-induced paw oedema, with the highest inhibitory effect exhibited by dK(Btn)P6. The inhibitory effect of D-Tyr-D-Lys-D-Asp-Gly tetrapeptide on PAF-induced paw oedema was much lower than that of Tyr-Lys-Asp-Gly tetrapeptide. In the experiments using tryptophan fluorescence spectroscopy, (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 bound to PAF dose-dependently, with dK(Btn)P6 showing the strongest binding affinity, indicating that its affinity appears to be closely correlated with its inhibitory effect on PAF-induced inflammation. These results suggest that direct binding of (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 to PAF can lead to marked inhibition of PAF-induced inflammation, and these agents, particularly dK(Btn)P6, may be useful as anti-inflammatory drugs targeting PAF with high stability in plasma.

Synthetic biotinylated peptide compounds derived from Asp-hemolysin: novel potent inhibitors of platelet-activating factor

Platelet-activating factor (PAF: 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a potent inflammatory mediator, is implicated in many inflammatory diseases and may possibly serve as a direct target for anti-inflammatory drugs. We have previously reported that Asp-hemolysin-related synthetic peptides (P4-P29) inhibit the bioactivities of oxidized low-density lipoprotein (ox-LDL) containing PAF-like lipids by direct binding to ox-LDL, which plays a key role in the atherosclerotic inflammatory process. In this study, we investigated whether these peptides inhibit the bioactivities of PAF by binding to PAF and its metabolite/precursor lyso-PAF. In in vitro experiments, P21, one of the peptides, bound to both PAF and lyso-PAF in a dose-dependent manner and markedly inhibited PAF-induced apoptosis in human umbilical vein endothelial cells. Moreover, in in vivo experiments, P4 and P21, particularly their N-terminally biotinylated peptide compounds (BP4 and BP21), inhibited PAF-induced rat paw oedema dose dependently and markedly, and showed sufficient inhibition of the oedema even at doses 150-300 times less than the doses of PAF antagonists. These results provide evidence that direct binding of N-terminally biotinylated peptide compounds derived from Asp-hemolysin to PAF and lyso-PAF leads to a dramatic inhibition of the bioactivities of PAF, both in vitro and in vivo, and strongly suggesting that these compounds may be useful as a novel type of anti-inflammatory drug for the treatment of several inflammatory diseases caused by PAF.

Anti-inflammatory effects of purine nucleosides, adenosine and inosine, in a mouse model of pleurisy: evidence for the role of adenosine A2 receptors

Adenosine and its metabolite, inosine, have been described as molecules that participate in regulation of inflammatory response. The aim of this study was to investigate the effect of adenosine and inosine in a mouse model of carrageenan-induced pleurisy as well as the participation of adenosine receptors in this response. Injection of carrageenan into the pleural cavity induced an acute inflammatory response characterized by leukocyte migration, pleural exudation, and increased release of interleukin-1β and tumor necrosis factor-α in pleural exudates. The treatment with adenosine (0.3-100 mg/kg, i.p.) and inosine (0.1-300 mg/kg, i.p.) 30 min before carrageenan injection reduced significantly all these parameters analyzed. Our results also demonstrated that A(2A) and A(2B) receptors seem to mediate the adenosine and inosine effects observed, since pretreatment with selective antagonists of adenosine A(2A) (ZM241385) and A(2B) (alloxazine) receptors, reverted the inhibitory effects of adenosine and inosine in pleural inflammation. The involvement of A(2) receptors was reinforced with adenosine receptor agonist CGS21680 treatment, since its anti-inflammatory effects were reversed completely and partially with ZM241385 and alloxazine injection, respectively. Moreover, the combined treatment with subeffective dose of adenosine (0.3 mg/kg) and inosine (1.0 mg/kg) induced a synergistic anti-inflammatory effect. Thus, based on these findings, we propose that inosine contributes with adenosine to exert anti-inflammatory effects in pleural inflammation, reinforcing the notion that endogenous nucleosides play an important role in controlling inflammatory diseases. This effect is likely mediated by the activation of adenosine A(2) subtype receptors and inhibition of production or release of pro-inflammatory cytokines.

Anti-inflammatory effects of a triterpenoid isolated from Wilbrandia ebracteata Cogn

Wilbrandia ebracteata (WE), a Brazilian medicinal plant used in folk medicine for the treatment of rheumatic diseases, displays anti-inflammatory properties and constitutes a rich source of cucurbitacins and cucurbitacin-related compounds. The current study investigated the potential anti-inflammatory properties of Dihydrocucurbitacin B (DHCB), a cucurbitacin-derived compound isolated from roots of WE, in some in vivo and in vitro experimental models. Intraperitoneal treatment of mice with DHCB reduced both carrageenan-induced paw edema (0.3, 1 and 3 mg/kg caused inhibitions of 26, 44 and 56 % at 2 h after stimulation, respectively) and pleurisy (10 mg/kg inhibited leukocyte numbers and LTB(4) levels in the pleural fluid by 51 and 75% at 6 h after cavity challenge, respectively). In vitro, DHCB (up to 10 microg/mL) failed to modify LTB(4) production by human neutrophils or PGE(2) production by COS-7 cells transfected with COX-1, but PGE(2) production by COX-2 transfected COS-7 cells was markedly inhibited (by 72%). The levels of COX-1 or COX-2 proteins in IL-1alpha-stimulated NIH3T3 cells were unaffected by DHCB. The results corroborate the potential anti-inflammatory properties ascribed to W. ebracteata Cogn. in folk medicine and suggest that they might be attributed, at least in part, to the capacity of one of this plants main constituents, DHCB, to inhibit COX-2 activity (but not its expression) during inflammation.

Association of Endothelin with Lung Hemorrhage Induced by Immune Complexes in Rats

The participation of endothelins (ETs) in a model of neutrophil-dependent lung injury induced by intrabronchial instillation of rabbit antibodies to ovalbumin followed by i.v. injection of the antigens (Arthus reaction) was investigated. Hemorrhagic lesions were evaluated by measuring the extravasations of hemoglobin in lung parenchyma. From 5 min to 24 h after the Arthus reaction (AR), endothelin (ir-ET) levels in bronchoalveolar lavage fluid (BALF) and in plasma were measured by radioimmunoassay. BALF levels of ir-ET were not different between control and AR animals for the first 90 min after the antigen challenge but increased from 2 to 24 h after induction of AR. ET levels in the plasma did not change from the respective controls over the same 24 h period. Increased ir-ET in BALF was not affected by pretreatment with L-NAME (30 mg/kg, i.v.). A PAF antagonist (BN52021; 5 and 10 mg/kg, i.v.) increased ET content in BALF and decreased the intensity of the AR. Thiorphan (2 mg/kg, i.v.) inhibited the AR-induced hemorrhagic lesions in lungs. An ET(A) receptor antagonist, BQ-123 (1 mg/kg, i.v.) potentiated, whereas the ET(B) antagonist, BQ-788 (1 mg/kg, i.v.) inhibited the lung hemorrhage. It is concluded that ETs are released during and play a role in the lung AR.

Effects of endothelin ETAreceptor antagonism on granulocyte and lymphocyte accumulation in LPS-induced inflammation

Endothelin peptides play active roles in different aspects of inflammation. This study investigates the contribution of endogenous endothelins to lipopolysaccharide (LPS) pulmonary inflammation by assessing the influence of ET(A) receptor antagonism on leukocyte accumulation, granulocyte adhesion molecule expression, and chemokine/cytokine modulation. Local pretreatment with BQ-123 or A-127722 (150 pmol), two selective and chemically unrelated endothelin ET(A) receptor antagonists, inhibits neutrophil and eosinophil accumulation in LPS-induced pleurisy at 24 h but not neutrophil migration at 4 h. The effect of endothelin antagonism on neutrophil accumulation at 24 h was concomitant with inhibition of eosinophil and CD4 and CD8 T lymphocyte influx. It is surprising that the ET(A) receptor blockade did not inhibit the accumulation of gammadelta T lymphocytes, cells that are important for granulocyte recruitment in this model. Blockade of ET(A) receptors did not influence the expression of adhesion molecules (CD11b, CD49d) on granulocytes but abrogated the increase in tumor necrosis factor alpha levels 4 h after LPS stimulation and also markedly inhibited increases in levels of interleukin-6 and keratinocyte-derived chemokine/CXC chemokine ligand 1 but not eotaxin/chemokine ligand 11. Thus, acting via ET(A) receptors, endogenous endothelins play an important role in early cytokine/chemokine production and on granulocyte and lymphocyte mobilization in LPS-induced pleurisy.

Effects of 5-aminoisoquinolinone, a water-soluble, potent inhibitor of the activity of poly (ADP-ribose) polymerase, in a rodent model of lung injury

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia--reperfusion injury and inflammation. The aim of the present study was to evaluate the effects of a novel and potent inhibitor of PARP activity on neutrophil recruitment in the acute inflammation induced by zymosan-activated plasma. Intra-thoracic administration of zymosan-activated plasma leads to an increase in neutrophil infiltration of the lung at 24hr. The potent PARP inhibitor 5-aminoisoquinolinone (5-AIQ) reduced the degree of lung injury and attenuated the expression of P-selectin and ICAM-1 as well as the recruitment of neutrophils into the injured lung. The up-regulation/expression of P-selectin and ICAM-1 in human endothelial cells exposed to oxidative stress (peroxynitrite) or to a pro-inflammatory cytokine (tumor necrosis factor alpha, TNFalpha) was also attenuated by 5-AIQ. These findings provide the first evidence that the activation of PARS participates in neutrophil-mediated lung injury by regulating the expression of P-selectin and ICAM-1.

Direct actions of endothelin-1 on single vessel hydraulic permeability

BACKGROUND

There is evidence that endothelin-1 (ET-1) increases extravasation of fluid and protein into vascular beds. The present study was designed to determine the direct effects of ET-1 on hydraulic permeability (Lp) when microvascular hydraulic and oncotic pressures are controlled.

METHODS

Postcapillary venules in the rat mesentery were perfused in situ and paired measurements of Lp obtained by using the modified Landis micro-occlusion method. Lp measured after a 15-minute perfusion with Ringer's albumin solution (control) was compared with Lp after a subsequent 15-minute perfusion with one of three treatments: control (n = 4), 8 pM ET-1 (n = 6), or 80 pM ET-1 (n = 6).

RESULTS

Baseline L for all vessels averaged (+/- SE) 8.1 +/-0.8 x 10(-8) cm x sec(-10 x cm H2O(-1) and was not significantly different between groups. Perfusion with either control or 8 pM ET-1 did not significantly change the Lp of any of the vessels. Significant decreases in Lp of 40 to 60% were observed in venules perfused with 80 pM ET-1. The average Lp in this group was 9.9 +/- 1.4 during baseline and decreased to 5.0 +/- 0.7 during ET-1 perfusion (p = 0.003). Washout of 80 pM ET-1 for periods of up to 15 minutes did not return Lp to baseline values.

CONCLUSION

Low-dose ET-1 did not directly increase Lp in postcapillary venules. ET-1 at 80 pM, however, significantly decreased Lp. These data implicate factors other than a direct permeability-increasing effect in ET-1. At higher concentrations, ET-1 may have a protective effect on endothelial barrier function.

In vitro and in vivo responses of murine granulocytes to human complement-derived, haemolytically inactive C5b67 (iC5b67)

Haemolytically inactive C5b67 (iC5b67), which was made from purified human components and decayed to a haemolytically inactive form, was evaluated as an agonist for murine leucocytes both in vitro and in vivo. In an in vitro assay, iC5b67 stimulated chemotaxis for both neutrophils purified from mouse bone marrow and splenic eosinophils of IL-5 transgenic mice. The stimulation was dose-dependent, with high dose inhibition. As with human neutrophils, iC5b67 also failed to up-regulate CR3 (CD11b/CD18) expression and to stimulate superoxide generation in murine bone marrow neutrophils, in vitro. In vivo, iC5b67 elicited an inflammatory response in a mouse model of pleuritis. A marked infiltration of neutrophils, which peaked at 4 h, was followed by an infiltration of eosinophils and mononuclear leucocytes. This inflammatory response was dose- and time-dependent. However, the protein concentration in the pleural wash fluid did not increase, indicating that iC5b67 did not induce a capillary leak. Although the infiltration of neutrophils could not be reproduced by pure C7 or human serum albumin (HSA), C5b6 did induce an influx of neutrophils. We were able to document the existence of C7, both antigenically and functionally, in pleural washes of normal mice, making it likely that the activity of C5b6 resulted from the in situ formation of C5b67 and iC5b67. The mouse model of pleuritis promises to be a useful in vivo system in which to evaluate the pro- and anti-inflammatory effects of iC5b67 that have been noted in vitro.

Anti-inflammatory effects of the products from Wilbrandia ebracteata on carrageenan-induced pleurisy in mice

Wilbrandia ebracteata Cogn. (Cucurbitaceae) is commonly known in Brazil as "Taiuia". The roots are employed in folk medicine for the treatment of several diseases, such as rheumatic disease. This study has evaluated the anti-inflammatory action of dicloromethane fraction (F-DCM), purified fraction (PFIII) and Cucurbitacin B extracted from crude extract of W. ebracteata in experimental models in vivo. The F-DCM (0.3 to 10 mg.kg(-1), i.p. or 3 to 30 mg.kg(-1) p.o.) produced significant but not dose-dependent inhibition of the carrageenan-induced cell influx and exsudate leakage in the pleural cavity of mice. The F-DCM 0.01 to 10 mg.kg(-1), i.p. or 0.1 to 10 mg.kg(-1) p.o.) decreased the levels of PGE2 in the exsudate leakage induced by carrageenan in the pleural cavity after 4 h with a calculated ID50 of 0.01 (0.002-0.09, i.p.) and 0.29 (0.05-1.45, p.o.) mg.kg(-1). The PFIII (3 mg.kg(-1), i.p.) inhibited 80% of cell migration (1.50 +/- 0.09 x 10(6) cells/cavity) and exsudate leakage by about 50% (3.09 +/- 0.71 microg/ml) in relation to the control group. Cucurbitacin B (0.1 mg.kg(-1), i.p.), the main compound of PFIII, reduced significantly the levels of PGE2 in the exsudate leakage by 40.7% (10.41 +/- 2.67 ng.ml(-1)). These data show that the active principle(s) present in the F-DCM of W. ebracteata elicited pronounced anti-inflammatory effects when assessed by i.p. or p.o. routes, as well as PFIII. The F-DCM was also able to prevent PGE2 formation in exsudate leakage induced by carrageenan, as well as Cucurbitacin B, its active principle. These results indicate that the anti-inflammatory activity of Wilbrandia ebracteata can be related with the inhibition of the production of PGE2.

Evaluation of anti-inflammatory-related activity of essential oils from the leaves and resin of species of Protium

The resins and leaves of species of Protium are commonly used by folk medicine. In the present study, we analyse the pharmacological effects of essential oils obtained by steam distillation (leaves and resin) from Protium species. Analysis by gas chromatography (GC) coupled to mass spectrometry and retention indices calculations demonstrate that the resin oil is constituted mainly of monoterpenes and phenylpropanoids: alpha-terpinolene (22%), p-cymene (11%), p-cimen-8-ol (11%), limonene (5%) and dillapiol (16%), whereas sesquiterpenes predominate as the volatile constituents of the leaves. The resin of Protium heptaphyllum (PHP) and leaves of P. strumosum (PS), P. grandifolium (PG), P. lewellyni (PL) and P. hebetatum (PHT) were screened for anti-inflammatory activity by the use of mouse pleurisy model induced by zymosan (500 microg/cavity) and lipopolysaccharide (LPS) (250 ng/cavity), for antinociceptive effect (by means of preventing mice abdominal writhings), as well as NO production from stimulated macrophages and proliferation of neoplasic cell lines: Neuro-2a (mouse neuroblastoma), SP2/0 (mouse plasmocytoma) and J774 (mouse monocytic cell line). The oils from PHP, PS and PL were able to inhibit protein extravasation but no sample inhibited total or differential leucocyte counts after administrating p.o. (100 mg/kg) 1 h before stimulation with zymosan. The oils from PG, PL and PHT inhibited neutrophil accumulation whereas PHP and specially PL inhibited LPS-induced eosinophil accumulation in mouse pleural cavity. PHT was also able to inhibit mononuclear cells accumulation. Antinociceptive effect was not observed, when animals received oral administration of the essential oils (100 mg/kg). In vitro treatment with essential oils (100 microg/well) changed the NO production from stimulated mouse macrophages. PHP inhibited in 74% and PS in 46% the LPS-induced NO production. In contrast, treatment with PL was able to increase in 49% the NO production. Cell lines proliferation was affected by the oils assayed in the range of 60-100% for Neuro-2a, 65-95% for SP2/0 and 70-90% for J774. Taken together these results showed that essential oils could be useful as efficient pharmacological tools.

Anti-inflammatory effects of theophylline, cromolyn and salbutamol in a murine model of pleurisy

1. The aim of this study was to examine the effect of theophylline, cromolyn and salbutamol, three well-known anti-asthmatic drugs, on the early (4 h) and late (48 h) phases of cell migration and fluid leakage induced by carrageenin in the pleural cavity of mice. 2. In the first set of experiments, animals were pretreated (30 min) with different doses of theophylline (0.5-50 mg kg-1, i.p.), cromolyn (0.02-0.2 mg per pleural cavity) or salbutamol (0.05-50 mg kg-1, i.p.); the total and differential cell content, and also the exudate were analysed 4 h after carrageenin (1%) administration. Afterwards, in order to evaluate the time course effects of these drugs on both phases of the inflammatory reaction, one dose employed in the above protocol was chosen, to pretreat (0.5-24 h) different groups of animals. The studied parameters were evaluated 4 and 48 h after pleurisy induction. 3. Acute administration of theophylline (1-50 mg kg-1, i.p.) cromolyn (0.02-0.2 mg per pleural cavity) and salbutamol (0.5-50 mg kg-1, i.p.), 30 min prior to carrageenin, caused significant inhibition of total cell and fluid leakage in the pleural cavity at 4 h (P < 0.01). All drugs exerted a long-lasting inhibitory effect on both exudation and cell migration (P < 0.01) when administered 0.5-8 h before pleurisy induction. However, the temporal profile of the inhibitory effect induced by these drugs on the first phase of the inflammatory reaction was clearly different. Thus, the inhibitory effect induced by theophylline and cromolyn on exudation was significantly longer (up to 24 h) in comparison to their effects on cell migration (only up to 8 h). In contrast, although salbutamol when administered 30 min before pleurisy induction abolished fluid leakage (P < 0.01), this effect was not sustained in the groups pretreated for 4-8 h. In these latter groups, a significant but much smaller reduction of exudation was observed (P < 0.01), whereas the magnitude of cell migration inhibition did not vary. 4. The second phase (48 h) of the inflammatory reaction induced by carrageenin (1%) was significantly inhibited by cromolyn (0.02 mg per pleural cavity) when this drug was administered 0.5-24 h before pleurisy induction (P < 0.01). Similar results were observed when theophylline (50 mg kg-1, i.p.) was administered 0.5-4 h before the injection of the phlogistic agent (P < 0.01). Treatment of the animals with salbutamol (5 mg kg-1, i.p.), 0.5-24 h before pleurisy induction, did not inhibit either cell migration or fluid leakage. In this condition, a significant increase of these parameters was observed in the group pretreated with salbutamol 8-24 h before pleurisy induction (P < 0.01). 5. These results indicate that theophylline and cromolyn were able to inhibit the early (4 h) and late (48 h) phases of the inflammatory reaction induced by carrageenin in a murine model of pleurisy. Salbutamol was effective only against the early phase. The inhibitory effects of theophylline, cromolyn and salbutamol on the early phase of this inflammatory reaction were long-lasting, although a distinct profile of inhibition was observed among them. These findings confirm and extend previous results described in other models of asthma and support both clinical and experimental evidence suggesting that these anti-asthmatic agents exhibit marked anti-inflammatory properties.

Anti-inflammatory properties of a platelet-activating factor acetylhydrolase

Platelet-activating factor (PAF) is a potent pro-inflammatory phospholipid that activates cells involved in inflammation. The biological activity of PAF depends on its structural features, namely an ether linkage at the sn-1 position and an acetate group at the sn-2 position. The actions of PAF are abolished by hydrolysis of the acetyl residue, a reaction catalysed by PAF acetylhydrolase. There are at least two forms of this enzyme--one intracellular and another that circulates in plasma and is likely to regulate inflammation. Here we report the molecular cloning and characterization of the human plasma PAF acetylhydrolase. The unique sequence contains a Gly-Xaa-Ser-Xaa-Gly motif commonly found in lipases. Recombinant PAF acetylhydrolase has the substrate specificity and lipoprotein association of the native enzyme, and blocks inflammation in vivo: it markedly decreases vascular leakage in pleurisy and paw oedema, suggesting that PAF acetylhydrolase might be a useful therapy for severe acute inflammation.

Cutaneous permeability responses to bradykinin and histamine in the guinea-pig: possible differences in their mechanism of action

1. Plasma protein extravasation (PPE) responses in guinea-pig skin have been measured using accumulation of intravenously injected 125I-labelled human serum albumin (125I-HSA). 2. The nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME; 0.1 mumol/site) significantly reduced responses to bradykinin (BK; 0.5 nmol/site) or histamine (4.5 nmol/site) when co-injected with the inflammatory mediators. D-NAME (0.1 mumol/site) had no significant effect. 3. L-NAME (0.01-0.1 mumol/site) appeared to produce greater shifts of the dose-response curve to BK (0.1-3 nmol/site) than of that to histamine (2.3-27 nmol/site). Both 0.01 and 0.1 mumol L-NAME/site significantly reduced the response to BK (0.5 nmol/site) whereas only the higher dose of L-NAME produced a significant reduction in the response to histamine (4.5 nmol/site). 4. The inhibitory effect of L-NAME (0.1 mumol/site) on the response to BK but not on that to histamine was significantly reversed by L-arginine (L-Arg; 10 mumol/site). D-arginine (D-Arg; 10 mumol/site) had no significant effect in either case. 5. L-Arg (10 mumol/site) significantly enhanced the response to BK but inhibited that to histamine. D-Arg (10 mumol/site) had no significant effect on BK but significantly inhibited histamine. L-Lysine (L-Lys: 10 mumol/site) had no significant effect on the response to either BK or histamine. 6. L-Arg (100 mM) had a significant inhibitory effect on isometric contractions to histamine, but not BK in guinea-pig ileum in vitro. D-Arg (100 mM) also significantly inhibited histamine responses whereas L-Lys (100 mM) had no effect. 7. The alpha-adrenoceptor agonist, phenylephrine (0.3 or 6 nmol/site) inhibited matched responses to BK (0.5 nmol/site) or histamine (5.4 nmol/site) to comparable degrees, but gave significant inhibition only at the higher dose. 8. The Beta-adrenoceptor agonist, isoprenaline (0.5 or 10 nmol/site) had a significant inhibitory effect on the response to histamine (5.4 nmol/site) whereas a comparable response to BK (0.5 nmol/site) was significantly reduced by the higher dose only.9. Our results with L-NAME suggest that local production of NO is involved in the modulation of mediator-induced vascular permeability. It is possible that NO may play a greater role in the extravasation response to BK than to that induced by histamine.10. The differential effects of L-NAME and isoprenaline on BK- and histamine-induced PPE raise the possibility that BK and histamine may induce vascular permeability via different mechanisms in guinea-pig skin.

Enhancement by endothelin-1 of microvascular permeability via the activation of ETA receptors

1. The objective of the present experiments was to assess the involvement of endothelin-A (ETA) receptors in mediating the effects of endothelin-1 on microvascular permeability in conscious rats. 2. Bolus injection of endothelin-1 (0.1 and 1 nmol kg-1, i.v.) resulted in a dose-dependent prolonged pressor effect preceded by a transient depressor response. These changes were accompanied by a dose-dependent loss of plasma volume. Endothelin-1 (1 nmol kg-1) enhanced the vascular permeability of the upper and lower bronchi, kidney, stomach, duodenum and spleen (up to 270%) as measured by the extravasation of Evans blue dye. 3. Pretreatment of the animals with the selective ETA receptor antagonist, BQ-123 (1 mg kg-1, i.v.) significantly blunted the pressor response to endothelin-1 without affecting the depressor response. BQ-123 inhibited by 87% the endothelin-1 (1 nmol kg-1)-induced plasma volume loss. BQ-123 markedly attenuated protein extravasation elicited by endothelin-1 in the upper and lower bronchi and kidney, whereas it completely inhibited the permeability effect of endothelin-1 in the stomach and duodenum. BQ-123 by itself had no significant effect on the parameters studied. 4. The endothelin-1 analogue, [Trp(For)21]-endothelin-1, in which Trp21 is formylated, was as potent a pressor agent as endothelin-1, but had no depressor action. Bolus injection of [Trp(For)21]-endothelin-1 (0.1 and 1 nmol kg-1, i.v.) evoked similar plasma volume losses to those observed following administration of equimolar doses of endothelin-1. Furthermore, 1 nmol kg-1 [Trp(For)21]-endothelin-l evoked increases in protein extravasation similar to endothelin-l, 1 nmol kg-1.5. The present findings suggest that endothelin- 1 enhances microvascular permeability, in part, via the activation of ETA receptors.