7-Epiclusianone, a tetraprenylated benzophenone, relaxes airway smooth muscle through activation of the nitric oxide-cGMP pathway.

This study was undertaken to investigate the putative mechanism(s) underlying the antispasmodic effect of 7-epiclusianone, a naturally occurring compound isolated from the plant Garcinia brasiliensis. Guinea pig tracheal rings were mounted in tissue baths filled with Krebs' solution, and the contractile response to distinct stimuli was measured in the presence or absence of 7-epiclusianone. We also tested the effect of 7-epiclusianone on methacholine-evoked airways obstruction in BALB/c mice using barometric plethysmography. 7-Epiclusianone (10 microM) inhibited epithelium-intact tracheal ring contraction induced by allergen, histamine, 5-hydroxytryptamine, or carbachol challenge. The relaxation effect was abrogated by epithelium removal, the presence of nitric-oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) (100 microM), or soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 microM). 7-Epiclusianone (1-100 microM) induced a dose-dependent increase in the intracellular cGMP levels of cultured tracheal rings. The relaxation effect of 7-epiclusianone was also inhibited by K(+) channel blockers tetraethylammonium (10 microM), glibenclamide (1 microM), or apamin (1 microM), but not by 9-(tetrahydro-2'-furyl)adenine (SQ22,536) (100 microM), an adenylate cyclase inhibitor. In epithelium-intact tracheal rings, 7-epiclusianone also inhibited Ca(2+)-induced contractions in K(+) (60 mM)-depolarized preparations, but it seemed ineffective in assays in which epithelium-denuded tracheal ring preparations were used. Oral administration of 7-epiclusinone (25-100 mg/kg) dose-dependently inhibited airway obstruction triggered by aerosolized methacholine (6-25 mg/ml), in a mechanism sensitive to L-NAME (20 mg/kg). In conclusion, the relaxation effect of 7-epiclusinone seems to be mediated by epithelium-, nitric oxide-, and cGMP-dependent mechanisms. Furthermore, oral administration of 7-epiclusianone reduces episodes of bronchial obstruction, warranting further research on this compound regarding a putative application in asthma therapy.

Local Administration of Gold Nanoparticles Prevents Pivotal Pathological Changes in Murine Models of Atopic Asthma.

Although gold nanoparticles have been shown to exhibit a range of beneficial biological properties, including antiinflammatory and anti-oxidant effects, their putative impact on allergic asthma has not been addressed. In this study, we evaluated the potential of nasal-instilled gold nanoparticles to prevent allergen-induced asthma in distinct murine models of this disease. Swiss-Webster (outbred) and A/J (inbred) mice were sensitized with ovalbumin and then treated with intranasal injections of gold nanoparticles (6 and 60 µg/kg), 1 h before ovalbumin challenges. Lung function, leukocyte infiltration, mucus exacerbation, extracellular matrix deposition, cytokine generation and oxidative stress were evaluated 24 h after the last challenge. In both mice strains, gold nanoparticles clearly inhibited (70-100%) allergen-induced accumulation of inflammatory cells as well as the production of both pro-inflammatory cytokines and reactive oxygen species. In A/J mice, recognized as genetic asthma prone animals, instilled gold nanoparticles clearly prevented mucus production, peribronchiolar fibrosis and airway hyper-reactivity triggered by allergen provocation. In conclusion, these findings demonstrate that gold nanoparticles prevented pivotal features of asthma, including airway hyper-reactivity, inflammation and lung remodelling. Such protective effects are accounted for by reduction in lung tissue generation of pro-inflammatory cytokines and chemokines, in a mechanism probably related to down-regulation in the levels of oxidative stress.

JMF2-1, a lidocaine derivative acting on airways spasm and lung allergic inflammation in rats.

BACKGROUND: Prior reports show that nebulized lidocaine might be an effective treatment for asthma. OBJECTIVE: We sought to determine the anti-inflammatory and spasmolytic effects of lidocaine and its analogue, JMF2-1, which we have synthesized for reduced local anesthetic activity. METHODS: Blockade of Na(+) currents was assayed in cultured GH(3) cells by using the patch-clamp technique, whereas anesthesia was assessed in a cutaneous pinching test in rats. Lidocaine and its analogue were nebulized into sensitized rats for evaluation of their effectiveness on airways spasm and inflammation induced by methacholine and allergen, respectively. Tissue histamine release and tracheal spasm triggered by allergen challenge in the absence and presence of these treatments were also examined in vitro. RESULTS: The 50% inhibitory concentration values for blockade of Na(+) currents after treatment with JMF2-1 (25.4 mM) was remarkably higher than that of lidocaine (0.18 mM), which is consistent with the weak anesthetic capacity of this analogue. In contrast, JMF2-1 was more potent than lidocaine in inhibiting allergen-induced histamine release and tracheal spasm. In in vivo settings methacholine-induced increase in lung resistance (145%) significantly reduced to 72% and 47% after lidocaine and JMF2-1 treatment, respectively. Both treatments inhibited by about 81% allergen-evoked eosinophil accumulation into the lung tissue. CONCLUSION: Replacement of the 2,6-dimethyl radicals by the 2-trifluormethyl group on the benzene ring of lidocaine significantly reduces anesthetic activity, preserving its ability to prevent key aspects of the allergic inflammatory response in the lung. CLINICAL IMPLICATIONS: Nebulized JMF2-1 might be a means of achieving the antiasthmatic effects of lidocaine without the anesthetic effects.

Histamine modulates mast cell degranulation through an indirect mechanism in a model IgE-mediated reaction.

Histamine is released in inflammatory reactions and exerts an immunoregulatory function on cells present in the microenvironment. In this study, we compared the effect of histamine on degranulation of mast cells derived from animals bearing a parasitic infection with those from uninfected animals. Peritoneal mast cells (PMC) were obtained 24 days after infection of Wistar rats with Toxocara canis. The degree of degranulation was assessed either morphologically or by measuring the release of beta-hexosaminidase and TNF-alpha. Non-purified PMC or mast cells immunomagnetically purified with mAb AA4 were used. An increase in degranulation of non-purified mast cells from infected animals was observed after incubation with histamine in vitro or when histamine was injected into the peritoneal cavity. When a purified mast cell population was used, this effect was no longer observed. Supernatants from spleen cells stimulated with histamine induced degranulation of purified mast cells, and again, this was potentiated with PMC from infected animals. However, when supernatants from peritoneal macrophages similarly stimulated were used, a reduction in the degranulation of PMC from infected animals was observed. Our results suggest that histamine may act as a regulator of mast cell degranulation, thus modulating inflammatory responses due to infection with certain parasites.