PTGS2 and idiopathic interstitial pneumonia: Another mechanism that favors the fibrotic process in IPF is changes in histones, for example, reduced histone H3 and H4 acetylation, which are associated with decreased cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE-2—a strong antifibrotic mediator) production by fibroblasts [32].