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Question:
A patient with asthma is being treated with a xanthine derivative such as theophylline. The drug relaxes smooth muscle in airways by which of the following mechanisms?
Correct Answer: D. Preventing cAMP degradation
Theophylline inhibits phosphodiesterase (PDE). PDE hydrolyzes and thus inactivates endogenous cAMP, therefore this is an (indirect) inhibitory effect of the drug. When theophylline blocks PDE, cAMP accumulates intracellularly; calcium uptake is promoted and calcium release from the SR is attenuated by a putative process involving cAMP-induced protein kinase A (PKA) activation.
Xanthine derivatives are also thought to function by increasing histone deacetyases (HDACs) activity. This removes acetylation from pro-inflammatory genes and thus reduces their expression (epigenetically).
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Category: PharmacologyA patient with asthma is being treated with a xanthine derivative such as theophylline. The drug relaxes smooth muscle in airways by which of the following mechanisms?
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