TY - JOUR
T1 - In vitro and ex vivo effects of the phosphodiesterase 4 inhibitor, rolipram, on thromboxane production in equine blood
AU - Rickards, K.J.
AU - Page, C.P.
AU - Lees, P.
AU - Gettinby, G.
AU - Cunningham, F.M.
PY - 2003/4
Y1 - 2003/4
N2 - Phosphodiesterase 4 (PDE4) inhibitors have been shown to inhibit equine neutrophil function in vitro and may be of benefit in recurrent airway obstruction (RAO), an allergy-based respiratory disease characterized by inflammatory cell recruitment and activation within the lungs following exposure of susceptible horses to allergens in mouldy hay. The aim of this study was to evaluate the inhibitory effects of the PDE4 inhibitor, rolipram, in an in vitro assay of thromboxane (Tx) production. The assay was then used to monitor the activity of this compound in vivo in normal and RAO-affected horses. Rolipram and the structurally distinct PDE4 inhibitor, denbufylline, attenuated both lipopolysaccharide (LPS)-induced and unstimulated Tx production in blood from normal horses. Thromboxane production appeared to involve a calcium-dependent interaction between leucocytes and platelets (LPS-induced Tx production = 2.3 ± 0.4, 4.5 ± 1.1 and 20.8 ± 3.6 ng/mL for platelets, leucocytes and blood, respectively) and rolipram-inhibited Tx production via an effect on leucocytes. Inhibition of ex vivo LPS induced Tx production was detected after intravenous administration of rolipram (5 μg/kg) to normal ponies. This dose did not significantly affect either lung function or neutrophil accumulation when administered to three horses with clinical signs of RAO. This study suggests that inhibition of Tx production in equine blood can be used to measure PDE4 activity. However, PDE4 inhibitors with improved therapeutic profiles are required for evaluation in RAO.
AB - Phosphodiesterase 4 (PDE4) inhibitors have been shown to inhibit equine neutrophil function in vitro and may be of benefit in recurrent airway obstruction (RAO), an allergy-based respiratory disease characterized by inflammatory cell recruitment and activation within the lungs following exposure of susceptible horses to allergens in mouldy hay. The aim of this study was to evaluate the inhibitory effects of the PDE4 inhibitor, rolipram, in an in vitro assay of thromboxane (Tx) production. The assay was then used to monitor the activity of this compound in vivo in normal and RAO-affected horses. Rolipram and the structurally distinct PDE4 inhibitor, denbufylline, attenuated both lipopolysaccharide (LPS)-induced and unstimulated Tx production in blood from normal horses. Thromboxane production appeared to involve a calcium-dependent interaction between leucocytes and platelets (LPS-induced Tx production = 2.3 ± 0.4, 4.5 ± 1.1 and 20.8 ± 3.6 ng/mL for platelets, leucocytes and blood, respectively) and rolipram-inhibited Tx production via an effect on leucocytes. Inhibition of ex vivo LPS induced Tx production was detected after intravenous administration of rolipram (5 μg/kg) to normal ponies. This dose did not significantly affect either lung function or neutrophil accumulation when administered to three horses with clinical signs of RAO. This study suggests that inhibition of Tx production in equine blood can be used to measure PDE4 activity. However, PDE4 inhibitors with improved therapeutic profiles are required for evaluation in RAO.
KW - obstructive pulmonary disease
KW - induced platelet aggregation
KW - in vitro
KW - tyrosine phosphorylation
KW - endothelial cells
KW - PDE4 inhibitor
KW - endotoxin
UR - http://dx.doi.org/10.1046/j.1365-2885.2003.00450.x
U2 - 10.1046/j.1365-2885.2003.00450.x
DO - 10.1046/j.1365-2885.2003.00450.x
M3 - Article
SN - 0140-7783
VL - 26
SP - 123
EP - 130
JO - Journal of Veterinary Pharmacology and Therapeutics
JF - Journal of Veterinary Pharmacology and Therapeutics
IS - 2
ER -