A rabbit model of hypersensitivity to plicatic acid, the agent responsible for red cedar asthma

In vivo models of occupational asthma due to low molecular weight chemicals

The aim was to review the development of in vivo models of asthma due to low molecular weight chemicals, in particular, those aspects that may be important to the understanding of occupational asthma in humans.

Mechanism of occupational asthma due to western red cedar (Thuja plicata)

Occupational asthma due to Western red cedar is the most common form of occupational asthma in the Pacific Northwest and affects 4-13.5% of the exposed population. It has been shown to be caused by plicatic acid, a low molecular weight compound present uniquely in the wood. The mechanism of asthma induced by plicatic acid is not known, as specific IgG antibodies were found only in about 20% of patients. Sera from patients with red cedar asthma failed to passively sensitize human lung fragments of human basophils. Basophils from patients with this disease released histamine when challenged directly with plicatic acid in a specific manner. Immunologic mechanisms other than Type I hypersensitivity reaction are likely to be involved.

Increased contraction and inositol phosphate formation of tracheal smooth muscle from hyperresponsive guinea pigs

Tracheal smooth muscle from guinea pigs with documented airway hyperresponsiveness in vivo after multiple antigen challenges produced 30% to 50% greater force than tracheas from control guinea pigs, when stimulated with carbachol, histamine, or leukotriene D4. When cultured smooth muscle cells were incubated with myo[2-3H]inositol, basal uptake of [3H]inositol was similar in cells from normal and hyperresponsive guinea pigs, but when these cells were stimulated with contractile agonists, there was increased uptake of inositol in hyperresponsive cells. Analysis of inositol phosphates by column chromatography and high-performance liquid chromatography revealed the presence of inositol-1,4,5-triphosphate, inositol-1,3,4-trisphosphate, inositol-1,4-bisphosphate, and inositol-1-monophosphate. The release of inositol-1,4,5-triphosphate, inositol-1,4-biphosphate, and inositol-1-monophosphate by smooth muscle cells stimulated with carbachol, leukotriene D4, or histamine was 20% to 40% greater in cells derived from hyperresponsive animals than cells from normal animals. These data demonstrate that the increased muscle contraction of hyperresponsive guinea pig tracheas is associated with increased inositol phosphate metabolism in these cells. Delineating the mechanisms of airway smooth muscle contraction should provide new pharmacologic targets for the inhibition of bronchoconstriction in asthma.

Specific immunological and bronchopulmonary responses following intradermal sensitization to free trimellitic anhydride in guinea pigs

We have developed a guinea pig model of trimellitic anhydride-induced airway hypersensitivity responses. In one group of guinea pigs, injected intradermally with 0.1 ml 30% trimellitic anhydride (TMA), we examined the specificity of the bronchopulmonary response to TMA comparing the effect of intravenous TMA conjugated to guinea pig serum albumin (GPSA) with a control hapten (procion dye) protein conjugate (PD-GPSA). A significant increase in pulmonary inflation pressure (PIP) was provoked in sensitized animals following intravenous injection with TMA-GPSA (20%; 0-400, median; range) as compared to intravenous injection of PD-GPSA. In the second group we compared three different methods of sensitization: single injection of 0.1 ml of 0.3% TMA; four injections of 0.1 ml of 0.1% TMA; and a single high dose injection of 30% TMA. Following intravenous TMA-GPSA guinea pigs sensitized with a single injection 0.3% TMA had an increase in PIP of 395%; 220-600, while those given four repeat injections of 0.1% TMA had an increase in PIP of 343%; 315-490. These results were significantly higher than the increase in PIP (160%; 0-220) which occurred in guinea pigs sensitized with a single dose of 30% TMA. Four of 11 guinea pigs given low dose injections of TMA had bronchopulmonary responses to inhaled TMA-GPSA. All sensitized guinea pigs had specific IgG1 antibodies demonstrated by enzyme linked immunosorbent assay (ELISA) and confirmed by ELISA inhibition. Four guinea pigs sensitized by low dose injections of TMA had IgE antibodies demonstrated by passive cutaneous anaphylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)