ATF1 and enteritis: TcdA stimulates cyclooxygenase-2 (COX-2) production via the p38 mitogen-activated protein kinase (MAPK)/mitogen- and stress-activated protein kinase (MSK-1)/cAMP response element binding protein (CREB)/activating transcription factor-1 (ATF-1) pathway, leading to prostaglandin E2 (PGE2) secretion, which promotes fluid secretion in TcdA-induced enteritis [157].