Tomato Lycopene Extract Prevents Lipopolysaccharide-Induced NF-κB Signaling but Worsens Dextran Sulfate Sodium-Induced Colitis in NF-κBEGFP Mice

BACKGROUND The impact of tomato lycopene extract (TLE) on intestinal inflammation is currently unknown. We investigated the effect of TLE on lipopolysaccharide (LPS)-induced innate signaling and experimental colitis. METHODOLOGY/PRINCIPAL FINDINGS Mice were fed a diet containing 0.5 and 2% TLE or isoflavone free control (AIN-76). The therapeutic efficacy of TLE diet was assessed using dextran sulfate sodium (DSS) exposed mice and IL-10(-/-);NF-kappaB(EGFP) mice, representing an acute and spontaneous chronic colitis model respectively. A mini-endoscope was used to determine the extent of macroscopic mucosal lesions. Murine splenocytes and intestinal epithelial cells were used to determine the in vitro impact of TLE on LPS-induced NF-kappaB signaling. In vitro, TLE blocked LPS-induced IkappaBalpha degradation, RelA translocation, NF-kappaB transcriptional activity and MIP-2 mRNA accumulation in IEC-18 cells. Moreover, LPS-induced IL-12p40 gene expression was dose-dependently inhibited in TLE-treated splenocytes. Interestingly, DSS-induced acute colitis worsened in TLE-fed NF-kappaB(EGFP) mice compared to control diet as measured by weight loss, colonoscopic analysis and histological scores. In contrast, TLE-fed IL-10(-/-);NF-kappaB(EGFP) mice displayed decreased colonic EGFP expression compared to control diet. IL-6, TNFalpha, and MCP-1 mRNA expression were increased in the colon of TLE-fed, DSS-exposed NF-kappaB(EGFP) mice compared to the control diet. Additionally, caspase-3 activation and TUNEL positive cells were enhanced in TLE diet-fed, DSS-exposed mice as compared to DSS control mice. CONCLUSIONS/ SIGNIFICANCE These results indicate that TLE prevents LPS-induced proinflammatory gene expression by blocking of NF-kappaB signaling, but aggravates DSS-induced colitis by enhancing epithelial cell apoptosis.