Quercetin acutely relaxes airway smooth muscle and potentiates β-agonist-induced relaxation via dual phosphodiesterase inhibition of PLCβ and PDE4

Am J Physiol Lung Cell Mol Physiol. 2013 Sep;305(5):L396-403. doi: 10.1152/ajplung.00125.2013. Epub 2013 Jul 19.


Asthma is a disease of the airways with symptoms including exaggerated airway narrowing and airway inflammation. Early asthma therapies used methylxanthines to relieve symptoms, in part, by inhibiting cyclic nucleotide phosphodiesterases (PDEs), the enzyme responsible for degrading cAMP. The classification of tissue-specific PDE subtypes and the clinical introduction of PDE-selective inhibitors for chronic obstructive pulmonary disease (i.e., roflumilast) have reopened the possibility of using PDE inhibition in the treatment of asthma. Quercetin is a naturally derived PDE4-selective inhibitor found in fruits, vegetables, and tea. We hypothesized that quercetin relaxes airway smooth muscle via cAMP-mediated pathways and augments β-agonist relaxation. Tracheal rings from male A/J mice were mounted in myographs and contracted with acetylcholine (ACh). Addition of quercetin (100 nM-1 mM) acutely and concentration-dependently relaxed airway rings precontracted with ACh. In separate studies, pretreatment with quercetin (100 μM) prevented force generation upon exposure to ACh. In additional studies, quercetin (50 μM) significantly potentiated isoproterenol-induced relaxations. In in vitro assays, quercetin directly attenuated phospholipase C activity, decreased inositol phosphate synthesis, and decreased intracellular calcium responses to Gq-coupled agonists (histamine or bradykinin). Finally, nebulization of quercetin (100 μM) in an in vivo model of airway responsiveness significantly attenuated methacholine-induced increases in airway resistance. These novel data show that the natural PDE4-selective inhibitor quercetin may provide therapeutic relief of asthma symptoms and decrease reliance on short-acting β-agonists.

Keywords: asthma; botanical; bronchodilator; flavonol; lung; phosphodiesterase 4; phospholipase Cβ.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetylcholine / pharmacology
  • Adrenergic beta-Agonists / pharmacology
  • Airway Resistance / drug effects
  • Animals
  • Antioxidants / pharmacology
  • Blotting, Western
  • Bronchoconstrictor Agents / pharmacology
  • Calcium / metabolism
  • Cells, Cultured
  • Cholinergic Agonists / pharmacology
  • Cyclic Nucleotide Phosphodiesterases, Type 4 / chemistry*
  • Cyclic Nucleotide Phosphodiesterases, Type 4 / metabolism
  • Humans
  • Inositol Phosphates / metabolism
  • Isoproterenol / pharmacology*
  • Male
  • Methacholine Chloride / pharmacology
  • Mice
  • Mice, Inbred A
  • Muscle Relaxation / drug effects*
  • Myocytes, Smooth Muscle / drug effects*
  • Myocytes, Smooth Muscle / metabolism
  • Nitric Oxide / metabolism
  • Phosphodiesterase 4 Inhibitors / pharmacology*
  • Phospholipase C beta / antagonists & inhibitors*
  • Phospholipase C beta / metabolism
  • Prostaglandins / metabolism
  • Quercetin / pharmacology*
  • Respiratory System / drug effects*
  • Respiratory System / metabolism
  • Type C Phospholipases / metabolism


  • Adrenergic beta-Agonists
  • Antioxidants
  • Bronchoconstrictor Agents
  • Cholinergic Agonists
  • Inositol Phosphates
  • Phosphodiesterase 4 Inhibitors
  • Prostaglandins
  • Methacholine Chloride
  • Nitric Oxide
  • Quercetin
  • Type C Phospholipases
  • Phospholipase C beta
  • Cyclic Nucleotide Phosphodiesterases, Type 4
  • Isoproterenol
  • Acetylcholine
  • Calcium