Dietary Tricin Suppresses Inflammation-Related Colon Carcinogenesis in Mice

Phytochemical profile and anti-inflammatory activity of the hull of γ-irradiated wheat mutant lines (Triticum aestivum L.)

Wheat (Triticum aestivum Linn.; Poaceae) is the second most cultivated food crop among all global cereal crop production. The high carbohydrate content of its grains provides energy, multiple nutrients, and dietary fiber. After threshing, a substantial amount of wheat hull is produced, which serves as the non-food component of wheat. For the valorization of these by-products as a new resource from which functional components can be extracted, the hull from the seeds of cultivated wheat mutant lines bred after γ-irradiation were collected. Untargeted metabolite analysis of the hull of the original cultivar (a crossbreeding cultivar., Woori-mil × D-7) and its 983 mutant lines were conducted using ultra-performance liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry technique. A total of 55 molecules were tentatively identified, including 21 compounds found in the Triticum species for the first time and 13 compounds not previously described. Among them, seven flavonolignans with a diastereomeric structure, isolated as a single compound from the hull of T. aestivum in our previous study, were used as the standards in the metabolite analysis. The differences in their collision cross-section values were shown to contribute to the clear distinction between tricine-lignan stereoisomers. To select functionally active agents with anti-inflammatory activity among the identified compounds, the wheat hull samples were evaluated for their inhibitory effect on nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells. As a result of multivariate analysis based on the results of chemical and biological profiles of the wheat hull samples, 10 metabolites were identified as key markers, contributing to the distinction between active and inactive mutant lines. Considering that one of the four key markers attributed to anti-inflammatory activity has been identified to be a flavonolignan, the wheat hull could be a valuable source of diverse tricin-lignan type compounds and used as a natural health-promoting product in food supplements.

Ethanol Extracts of Rice Bran and Whole Grain Adlay Seeds Mitigate Colonic Inflammation and Damage in Mice with Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease with frequent relapsing inflammation in the colon. Whole grains have been promoted as healthy and sustainable foods; however, the use of whole gains in UC is inconclusive. The aim of this study was to investigate the effects of ethanol extracts of rice bran (RBE) and whole-grain adlay seeds (ADE) on inflammation, oxidative stress, and colonic damage in UC. Male C57BL/6JNarl mice were intra-rectal injected twice with 2,4-dinitrobenzene sulfonic acid to induce (day 0) and reactivate (day 21) UC. Control mice were fed AIN-93M diet (R group) and injected with a vehicle. UC mice were fed AIN-93M diet (UC group) supplemented with RBE (RBE group) or ADE (ADE group) for 21 days. The results showed that the UC group had an increased disease activity index, plasma interleukin (IL)-6 and glutathione levels, microscopic injury scores, and inflammatory cytokine and chemokine levels in the colon and decreased colonic claudin-4 compared to the R group. RBE and ADE supplementation significantly reduced UC-elevated plasma IL-6 and colonic glutathione and pro-inflammatory cytokines and a chemokine. In addition, RBE and ADE supplementation significantly decreased T-helper-cell-associated cytokines in the plasma and colon. Moreover, RBE supplementation increased colonic IL-10 and tight junction protein claudin-4 levels, and ADE supplementation alleviated diarrhea in UC mice. In conclusion, these results suggest that RBE and ADE may mitigate colonic inflammation, oxidative stress, and damage in UC relapse.

Natural flavone tricin exerted anti-inflammatory activity in macrophage via NF-κB pathway and ameliorated acute colitis in mice

BACKGROUND

Ulcerative colitis is a subtype of inflammatory bowel disease, characterized by relapsing inflammation in the gastrointestinal tract with limited treatment options. Previous studies suggested that the natural compound tricin, a flavone isolated from rice bran, could suppress chemically-induced colitis in mice, while our recent study also demonstrated the anti-metastatic effect of tricin in colon tumor-bearing mice.

HYPOTHESIS/PURPOSE

Here we further investigated the underlying mechanism of the inhibitory effects of tricin on lipopolysaccharides-activated macrophage RAW264.7 cells and explored the efficacy of tricin in acute colitis mouse model induced by 4.5% dextran sulfate sodium (DSS) for 7 days.

METHODS

Tricin (75, 100, and 150 mg/kg) or the positive control drug sulfasalazine (200 mg/kg) were orally administered to mice for 7 days. Stool consistency scores, stool blood scores, and body weight were recorded daily. Disease activity index (DAI) was examined on day 7, and colon tissues were collected for biochemical analyses. The fecal microbiome of colitis mice after tricin treatment was characterized for the first time in this study using 16S rDNA amplicon sequencing.

RESULTS

Results showed that tricin (50 µM) remarkably reduced nitric oxide production in lipopolysaccharides-activated RAW264.7 cells and the anti-inflammatory activity of tricin was shown to act through the NF-κB pathway. Besides, tricin treatment at 150 mg/kg significantly reversed colon length reduction, reduced myeloperoxidase activities and DAI scores, as well as restored the elevated myeloid-derived suppressive cells population in acute colitis mice. The influence from DSS on gut microbiota, such as the increased population of Proteobacteria phylum and Ruminococcaceae family, was shown to be relieved after tricin treatment.

CONCLUSION

Our present study firstly demonstrated that tricin ameliorated acute colitis by improving colonic inflammation and modulating gut microbiota profile, which supports the potential therapeutic use of tricin for colitis treatment.

Tricin Biosynthesis and Bioengineering

Tricin (3',5'-dimethoxyflavone) is a specialized metabolite which not only confers stress tolerance and involves in defense responses in plants but also represents a promising nutraceutical. Tricin-type metabolites are widely present as soluble tricin O-glycosides and tricin-oligolignols in all grass species examined, but only show patchy occurrences in unrelated lineages in dicots. More strikingly, tricin is a lignin monomer in grasses and several other angiosperm species, representing one of the "non-monolignol" lignin monomers identified in nature. The unique biological functions of tricin especially as a lignin monomer have driven the identification and characterization of tricin biosynthetic enzymes in the past decade. This review summarizes the current understanding of tricin biosynthetic pathway in grasses and tricin-accumulating dicots. The characterized and potential enzymes involved in tricin biosynthesis are highlighted along with discussion on the debatable and uncharacterized steps. Finally, current developments of bioengineering on manipulating tricin biosynthesis toward the generation of functional food as well as modifications of lignin for improving biorefinery applications are summarized.