TNF and colitis: Furthermore, protocatechuic acid-treated mice exhibited a reduction in the expression of proinflammatory cytokines (IL-6, IL-1β, TNF-α, and cyclooxygenase 2 (COX-2)) in TNBS-induced colitis, achieved by modulating the sphingosine kinase (SphK)/S1P and related signaling pathways [18].