PTGS2 and depressive disorder: This enzyme is produced by macrophages and microglia and can produce neuroactive tryptophan metabolites which induce depression-like behavior.24 Cyclooxygenase-2 (COX-2) induces production of prostaglandins in inflammation.25 The effect of celecoxib as a selective COX-2 inhibitor in treatment of depression has been widely studied in numerous studies.