Endothelin ==> vasoconstrictor of endothelial cells
(makes ENDOTHELial cells go IN to the lumen --> vasoconstrictor)
COPD is usually associated with Pulmonary Hypertension. The examiner tells you that there is a loud pulmonary component of S2 ie: P2 (Loud S2/P2= Pulmonary Hypertension). Fev1:FVC is just related to COPD. The question is asking what is DECREASED in the pulmonary VASCULAR SMOOTH MUSCLE. do not get confused with the line stating there is decreased diffusing capacity for CO. the question isn't asking about that.
In pulmonary hypertension there is an imbalance between vasodilation substances and vasoconstrictors.
therefore our vasodilators would be decreased eg: Nitric Oxide
if it asked increased, you could go with Endothelin (remember the endothelin antagonists used for t/t of Pulm HTN ie: bosentan
sorry gave some extra info but all of it is important because they can ask this concept in many ways