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).


CONCLUSIONS
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.
Dacre
K J
KJ
Department of Veterinary Clinical Sciences, Easter Bush Veterinary Centre, Royal (Dick) School of Veterinary Studies, Midlothian, UK. K.J.Dacre@massey.ac.nz
McGorum
B C
BC
Marlin
D J
DJ
Bartner
L R
LR
Brown
J K
JK
Shaw
D J
DJ
Robinson
N E
NE
Deaton
C
C
Pemberton
A D
AD
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D016022:Case-Control Studies; D004391:Dust; D004848:Epithelium / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006736:Horses / Q000378:metabolism*; D007150:Immunohistochemistry; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology*; D009930:Organic Chemicals / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D053802:Tryptases / Q000235:genetics / Q000378:metabolism*
D004391:Dust; D009930:Organic Chemicals; D012333:RNA, Messenger; D053802:Tryptases