Intratracheal dosing with disodium cromoglycate inhibits late asthmatic response by attenuating eicosanoid production in guinea pigs

In vitro study of disodium cromoglicate as a novel effective hydrotrope solvent for hypericin utilisation in photodynamic therapy

Hypericin (HY) is a naphthodianthrone that naturally occurs in Hypericum perforatum L. It is a promising photosensitiser used in photodynamic therapy for and diagnosis of oncological diseases. However, its hydrophobic character is an obstacle that has prevented its efficient use. The commonly used solvent, dimethyl sulfoxide (DMSO), is a controversial constituent of HY formulations and its use has been rejected by many researchers studying HY both in vitro and in vivo. In this study, we propose the utilisation of hydrotropy to solubilise HY in an aqueous environment. Cromolyn (DSCG) is a non-toxic, well-tolerated, antiallergic drug that has been employed in clinical practice since 1970, and in aqueous solution it acts as a hydrotrope. At a molecular ratio of 1:12,000 HY to DSCG, the compound is able to solubilise HY in aqueous environment. In an HT-29 cell suspension, DSCG (1.8 mmol L-1) considerably enhances the interaction between HY (150 nmol L-1) and HT-29 cells, which leads to an HY fluorescence emission increase with a half-time approximately 2 min compared to 29 min for samples that lack DSCG. Studies using HT-29 adenocarcinoma cells showed that DSCG at a given concentration significantly improved accumulation of HY within cells compared to DMSO (p < 0.05) despite the relative resistance of the HT-29 cell line to HY-PDT. Though no significant difference between total reactive oxygen species production was observed for photoactivated HY dissolved in DMSO and DSCG, significant singlet oxygen generation by photoactivated HY dissolved in a DSCG-containing water solution at the studied molecular ratio was confirmed. We also clarified that DSCG does not act as a scavenger of ABTS and galvinoxyl free radicals. The results from an MTT assay showed that DSCG also significantly enhanced the cytotoxicity of photoactivated HY compared to DMSO (p < 0.05). This study has demonstrated the ability of DSCG to act as a solvent of HY and enhance the effectiveness of HY-PDT compared to the commonly used organic solvent, DMSO.

Intratracheal sensitization/challenge-induced biphasic asthmatic response and airway hyperresponsiveness in guinea pigs

In most experimental model of asthma using guinea pigs, the animals are made to inhale an aerosolized antigen which passes through the nasal cavity. In the present study, we attempted to create an animal model of asthma showing a biphasic asthmatic response and airway hyperresponsiveness, in which the allergic responses are restricted to the lung. Guinea pigs were sensitized by the intratracheal instillation of ovalbumin (OVA)+Al(OH)₃ once a day for 7 d, and then intratracheally challenged with OVA 12 d after the last sensitization. The change in specific airway resistance (sRaw) and airway responsiveness to histamine were measured. Pranlukast (100 mg/kg), theophylline (50 mg/kg), and dexamethasone (10 mg/kg) were orally administered 18 and 2 h before the antigen challenge. The challenge caused a marked biphasic elevation of sRaw with peaks at 5 min and 4 h. At 24 h, airway hyperresponsiveness to histamine was observed. Pranlukast, theophylline, and dexamethasone suppressed the late asthmatic response and airway hyperresponsiveness. The early asthmatic response was inhibited by theophylline and dexamethasone. In conclusion, the intratracheal sensitization and challenge caused a biphasic asthmatic response and airway hyperresponsiveness in guinea pigs. This model may be useful for the evaluation of anti-asthma drugs.

Pulmonary emphysema induced by cigarette smoke solution and lipopolysaccharide in guinea pigs

Exposure of animals to cigarette smoke for longer than 3 months leads to the development of chronic obstructive pulmonary disease (COPD) showing pulmonary emphysema. We attempted to create a COPD model with emphysema that could be established in a shorter period of time. Guinea pigs were intratracheally treated once a day on days 0-3, 5-8, 10-13 and 15-18 with a cigarette smoke solution (CSS), which was prepared by bubbling a stream of smoke into saline. Additionally, lipopolysaccharide (LPS) was administered intratracheally as an exacerbation factor on days 4, 9 and 14. By day 19, there was a gradual elevation of specific airway resistance (sRaw). In addition, both residual volume and functional residual capacity were found to be significantly higher on day 19. In the lungs, there was a marked increase in leukocytes, especially neutrophils. Histologically, we observed epithelial hyperplasia and emphysema. On the other hand, daily oral administration of theophylline during the administration of CSS and LPS suppressed the sRaw increase and the epithelial hyperplasia, but not other functional structural changes. In conclusion, we established an experimental COPD model in guinea pigs by using intratracheal instillations of CSS and LPS over a considerably shorter term than has been reported for other models.

The mast cell and allergic diseases: role in pathogenesis and implications for therapy

Mast cells have long been recognized for their role in the genesis of allergic inflammation; and more recently for their participation in innate and acquired immune responses. Mast cells reside within tissues including the skin and mucosal membranes, which interface with the external environment; as well as being found within vascularized tissues next to nerves, blood vessels and glandular structures. Mast cells have the capability of reacting both within minutes and over hours to specific stimuli, with local and systemic effects. Mast cells express the high affinity IgE receptor (FcepsilonRI) and upon aggregation of FcepsilonRI by allergen-specific IgE, mast cells release and generate biologically active preformed and newly synthesized mediators which are involved in many aspects of allergic inflammation. While mast cells have been well documented to be essential for acute allergic reactions, more recently the importance of mast cells in reacting through pattern recognition receptors in innate immune responses has become recognized. Moreover, as our molecular understanding of the mast cell has evolved, novel targets for modulation have been identified with promising therapeutic potential.

Delayed-type asthmatic response induced by repeated intratracheal exposure to toluene-2,4-diisocyanate in guinea pigs

BACKGROUND

A toluene-2,4-diisocyanate (TDI)-induced asthma model, in which delayed-type hypersensitivity-like asthmatic airway obstruction is elicited restrictively in the lung, has never been developed.

METHODS

Guinea pigs were percutaneously sensitized with TDI. For the challenges, once every 2 weeks for a total of 5 times, TDI mists were delivered directly to the lung through an oral cannula, with its tip being positioned in the opening of the trachea. Time-course changes in specific airway resistance (sRaw) were measured by double-flow plethysmography. Basic mechanisms underlying TDI-induced asthma were analyzed.

RESULTS

After the 2nd-5th challenges, induction of both an early increase in sRaw that peaked at 10 min and a delayed-type sRaw elevation that peaked at 22 h were observed. Interestingly, in the sensitized/challenged animals, baseline sRaw was elevated by repeated challenge as compared to that seen for non-sensitized animals. Intratracheal administration of a bronchodilator, salbutamol, strongly suppressed the early asthmatic response (EAR) but not the delayed-type asthmatic response (DAR). During DAR, both albumin leakage and fucose secretion into the bronchoalveolar lavage fluid were increased. The cysteinyl leukotriene antagonist pranlukast failed to inhibit either EAR or DAR while the corticosteroid dexamethasone significantly suppressed DAR, without significantly affecting EAR.

CONCLUSIONS

Effective delivery of TDI to the lung may induce reproducible DAR in sensitized guinea pigs with chronicity that is reflected by an increase in the sRaw baseline. DAR is not mediated by constriction of airway smooth muscles and is probably due to the concurrent presence of mucosal edema and mucus hypersecretion in the airways.