cDNA cloning and substrate specificity of equine tryptase, a possible mediator in equine heaves

Involvement of mast cells and proteinase-activated receptor 2 in oxaliplatin-induced mechanical allodynia in mice

The chemotherapeutic agent oxaliplatin induces neuropathic pain, a dose-limiting side effect, but the underlying mechanisms are not fully understood. Here, we show the potential involvement of cutaneous mast cells in oxaliplatin-induced mechanical allodynia in mice. A single intraperitoneal injection of oxaliplatin induced mechanical allodynia, which peaked on day 10 after injection. Oxaliplatin-induced mechanical allodynia was almost completely prevented by congenital mast cell deficiency. The numbers of total and degranulated mast cells was significantly increased in the skin after oxaliplatin administration. Repetitive topical application of the mast cell stabilizer azelastine hydrochloride inhibited mechanical allodynia and the degranulation of mast cells without affecting the number of mast cells in oxaliplatin-treated mice. The serine protease inhibitor camostat mesilate and the proteinase-activated receptor 2 (PAR2) antagonist FSLLRY-NH2 significantly inhibited oxaliplatin-induced mechanical allodynia. However, it was not inhibited by the H1 histamine receptor antagonist terfenadine. Single oxaliplatin administration increased the activity of cutaneous serine proteases, which was attenuated by camostat and mast cell deficiency. Depletion of the capsaicin-sensitive primary afferents by neonatal capsaicin treatment almost completely prevented oxaliplatin-induced mechanical allodynia, the increase in the number of mast cells, and the activity of cutaneous serine proteases. These results suggest that serine protease(s) released from mast cells and PAR2 are involved in oxaliplatin-induced mechanical allodynia. Therefore, oxaliplatin may indirectly affect the functions of mast cells through its action on capsaicin-sensitive primary afferents.

Organic dust exposure increases mast cell tryptase in bronchoalveolar lavage fluid and airway epithelium of heaves horses

BACKGROUND

Mast cell degranulation is believed to act as a key event in initiating and maintaining airway response to allergen challenge in human asthma. It is hypothesized that the mast cell may play a similar role in equine heaves, which shares many similarities with occupational dust-induced asthma.

OBJECTIVE

The aim of this study was to quantify the mast cell proteinase tryptase in bronchoalveolar lavage fluid (BALF) from control and heaves-susceptible horses and to investigate tryptase mRNA and protein expression in pulmonary mast cells.

METHODS

Equine BALF tryptase concentrations were determined by ELISA from control and heaves-susceptible horses pre and post 24 h hay/straw challenge (HSC). Tryptase mRNA and protein expression were investigated by quantitative PCR and immunohistochemistry in bronchial and bronchiolar tissue samples of control and heaves-susceptible horses.

RESULTS

Both control and heaves-susceptible horses had significantly increased BALF tryptase concentrations following HSC (P=0.003 and 0.034, respectively). Increased numbers of tryptase-expressing intra-epithelial mast cells were demonstrated in heaves horses, but not controls, following challenge (P=0.02). Bronchiolar tissue from heaves horses removed from challenge contained significantly lower tryptase transcripts than that from control horses (P=0.02).

CONCLUSION

Mast cell degranulation and tryptase release into the airways occur following HSC of control and heaves-susceptible horses. The greater number of mast cells available in the bronchiolar epithelium of heaves horses may be clinically significant in the pulmonary inflammatory response of heaves.