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The Function of β‐carotene on Colonic Inflammation and Gut Barrier Integrity
Author(s) -
Balbuena Emilio,
Cheng Junrui,
Miller Baxter,
Neilson Andrew,
Ferruzzi Mario,
Eroglu Abdulkerim
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.04076
Subject(s) - occludin , barrier function , carotenoid , caco 2 , tlr4 , tumor necrosis factor alpha , receptor , inflammation , lipopolysaccharide , tight junction , microbiology and biotechnology , chemistry , biology , biochemistry , in vitro , immunology
Background Carotenoids are naturally occurring pigments accounting for brilliant colors of fruits and vegetables. Dietary carotenoids can exert anti‐inflammatory properties in humans. Carotenoids are absorbed in the small intestine. A significant amount of the carotenoids may escape absorption and can be transferred to the colon. Carotenoids can be further released, or additional conversions can happen within colon epithelial cells, colonocytes. Objective A major research gap exists regarding the effects of dietary carotenoids in the colonocytes. We propose to address it by examining the effects of major dietary carotenoid, β‐carotene (BC), in colonocytes. Our central hypothesis is that BC can modulate the inflammatory transcription factor, nuclear factor‐kappa B (NF‐κB). Methods To address our hypothesis, we examined the function of BC in the lipopolysaccharide (LPS)/toll‐like receptor (TLR4) signaling pathway using in vitro human colon epithelial cell model. First, HT‐29 cells were primed with interferon‐γ, then subjected to LPS and BC at the same time. Subsequently, we employed western blotting to biochemically evaluate expressions of TLR4 and its co‐receptor, CD14. Additionally, we examined the signals of NF‐κB p65 subunit. We also studied the impact of BC on the essential tight junction proteins, including claudin‐1 and occludin. Then, we employed another analytical biochemistry assay, enzyme‐linked immunosorbent assay (ELISA) to illustrate the effect of BC on the release of pro‐inflammatory cytokines such as interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), and tumor necrosis factor alpha (TNFα). Next, we decided to perform immunocytochemistry experiments to visualize the signals of claudin‐1. Finally, we used high‐performance liquid chromatography, C30 reversed‐phase column, a mobile phase of methanol, methyl‐tert‐butyl‐ether, and acetonitrile with gradient separation and visible detection at 475 nm to separate BC in cell culture supernatants. Results β‐Carotene was found to decrease LPS‐induced intestinal inflammation in colonocytes. It also enhanced gut barrier function via promoting the levels of tight junction proteins, both qualitatively and quantitatively. ELISA assays demonstrated that BC reduced the release of pro‐inflammatory cytokines. Finally, HPLC portrayed that the anti‐inflammatory activity of BC was mostly stemming from itself. Conclusions Overall, this study's findings suggest that BC could be a bioactive compound within colonocytes as it could be an effective player in colonic inflammation. BC could also buttress the intestinal barrier integrity when colonocytes were challenged with LPS. These findings will enhance our knowledge of how BC functions in colonic inflammation and its role in gut barrier integrity.