Leflunomide prevents alveolar fluid clearance inhibition by respiratory syncytial virus.
BACKGROUND
Previously, we demonstrated that intranasal infection of BALB/c mice with respiratory syncytial virus (RSV) resulted in an early 40% reduction in alveolar fluid clearance (AFC), an effect mediated via P2Y purinergic receptors.


OBJECTIVE
To confirm that RSV-induced inhibition of AFC is mediated by uridine triphosphate (UTP), and to demonstrate that inhibition of de novo pyrimidine synthesis with leflunomide prevents increased UTP release after RSV infection, and thereby also prevents inhibition of AFC by RSV.


METHODS
BALB/c mice were infected intranasally with RSV strain A2. AFC was measured in anesthetized, ventilated mice by instillation of 5% bovine serum albumin into the dependent lung. Some mice were pretreated with leflunomide or 6-mercaptopurine.


RESULTS
RSV-mediated inhibition of AFC is associated temporally with a 20-nM increase in UTP and ATP content of bronchoalveolar lavage fluid, hypoxemia, and altered nasal potential difference. RSV-mediated nucleotide release, AFC inhibition, and physiologic sequelae thereof can be prevented by pretreatment of mice with the de novo pyrimidine synthesis inhibitor leflunomide, which is not toxic to the mice, and which does not affect RSV replication in the lungs. In contrast, pretreatment of mice with 6-mercaptopurine, an inhibitor of de novo purine synthesis, has no beneficial effect on AFC or other indicators of disease progression. Finally, RSV-mediated inhibition of AFC is prevented by volume-regulated anion channel inhibitors.


CONCLUSIONS
Pyrimidine synthesis or release pathways may provide novel therapeutic targets to counter the pathophysiologic sequelae of impaired AFC in RSV disease.
Davis
Ian C
IC
Department of Anesthesiology, University of Alabama at Birmingham, 224 BMR II, 901 South 19th Street, Birmingham, AL 35205-3703, USA.
Lazarowski
Eduardo R
ER
Hickman-Davis
Judy M
JM
Fortenberry
James A
JA
Chen
Fu-Ping
FP
Zhao
Xiaodong
X
Sorscher
Eric
E
Graves
Lee M
LM
Sullender
Wayne M
WM
Matalon
Sadis
S
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology*; D004195:Disease Models, Animal; D018450:Disease Progression; D005260:Female; D007555:Isoxazoles / Q000494:pharmacology*; D000077339:Leflunomide; D008168:Lung / Q000378:metabolism / Q000473:pathology / Q000821:virology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009708:Nucleotidases / Q000378:metabolism; D011024:Pneumonia, Viral / Q000188:drug therapy* / Q000378:metabolism / Q000821:virology; D018357:Respiratory Syncytial Virus Infections / Q000188:drug therapy* / Q000378:metabolism / Q000821:virology; D012136:Respiratory Syncytial Viruses / Q000472:pathogenicity*; D012720:Severity of Illness Index
D000998:Antiviral Agents; D007555:Isoxazoles; D009708:Nucleotidases; D000077339:Leflunomide