Timing-dependent protective and therapeutic effects of ethyl pyruvate in trinitrobenzene sulfonic acid-induced experimental colitis.

Ulcerative colitis (UC) involves excessive inflammation, extracellular matrix remodelling and oxidative stress. Ethyl pyruvate (EP) exhibits anti-inflammatory effects, but the comparative efficacy of prophylactic versus therapeutic administration and timing-dependent molecular responses remains unclear. The objective of this work was to evaluate timing-dependent protective and therapeutic effects of EP in trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis, focusing on inflammatory mediators, matrix metalloproteinases (MMPs), oxidative status and gene expression. Rats were randomly assigned to Control, EP, Colitis, Pre-colitis (EP before TNBS) and Post-colitis (EP after TNBS) groups. Colonic injury was assessed macroscopically and histopathologically. Tissue levels of matrix metalloproteinase (MMP)-2, MMP-9, interleukin (IL)-1, IL-17, IL-10, nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS) and total antioxidant capacity (TAC) were measured using ELISA kits. Gene expression of MMP-9, cytokines, NF-κB, high mobility group box 1 (HMGB1), iNOS and interferon-γ was analysed by quantitative real-time PCR. TNBS induced severe colonic injury with upregulation of pro-inflammatory cytokines, NF-κB signalling, MMP-2/9 and oxidative imbalance (P < 0.01). EP attenuated tissue damage in both prophylactic and therapeutic settings. Post-colitis (therapeutic) EP administration produced greater suppression of MMP-2, MMP-9, NF-κB, HMGB1 and iNOS, along with superior restoration of TAC (P < 0.05), indicating timing-dependent modulation of inflammatory and matrix degradation pathways. EP exerts both preventive and therapeutic effects in TNBS-induced colitis by suppressing inflammatory signalling, regulating extracellular matrix remodelling and enhancing antioxidant defences. Therapeutic administration is more effective than prophylactic treatment, highlighting the importance of timing in optimizing EP's efficacy in inflammatory bowel disease.