Inflammation In Caco-2 Cells Research Articles

Kjellmaniella crassifolia Reduces Lipopolysaccharide-Induced Inflammation in Caco-2 Cells and Ameliorates Loperamide-Induced Constipation in Mice.

Gastrointestinal disorders are widespread globally, with inflammatory diseases being particularly prominent. This study aimed to investigate the effect of Kjellmaniella crassifolia hot water extract (KCH) on lipopolysaccharide (LPS)-induced inflammation in human intestinal epithelial (Caco-2) cells and loperamide-induced constipation in BALB/c mice. The study's findings revealed that KCH dose-dependently increased the cell viability and reduced the NO production by decreasing the iNOS and COX-2 expression in LPS-stimulated Caco-2 cells. Also, KCH downregulated the mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α) by regulating the activation of MAPK and NF-κB signaling pathways in LPS-stimulated Caco-2 cells. In addition, KCH increased the expression levels of tight junction proteins, occludin, ZO-1, and claudin-1 in a dose-dependent manner. Furthermore, in vivo study outcomes demonstrated that KCH improved intestinal transit, increased fecal moisture content, and reduced fecal impaction in constipated mice. KCH decreased the mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α), thereby increasing the expression levels of intestinal tight junction proteins (occludin, ZO-1, and claudin-1) in the small intestine tissues of the experimental mice. These proteins may help regulate intestinal motility and improve stool passage, thus reducing constipation. These findings suggest that KCH could be a promising functional food ingredient for managing intestinal inflammation, inflammation-related disorders, constipation, and the pathophysiology of constipation.

METTL14 is Involved in TNF-α-Induced Inflammation in Colorectal Epithelial Cells via Autophagy Modulation.

Ulcerative colitis (UC) is a chronic and relapsing inflammatory bowel disease (IBD) characterized by colorectal inflammation. The N6-methyladenosine (m6A) modification of RNA regulates gene expression through the modulation of RNA metabolism, thus influencing various physiological and pathological processes. The aim of this study was to investigate the biological function of m6A methyltransferase METTL14 in colorectal epithelial cell inflammation. Bioinformatics analysis indicated that METTL14 expression was decreased in UC and was associated with disease severity and immune infiltration. We also noted a downregulation of METTL14 expression and a decrease in the total m6A RNA levels in TNF-α-stimulated Caco-2 cells. Moreover, METTL14 knockdown promoted inflammation and inhibited autophagy in TNF-α-stimulated Caco-2 cells, as indicated by the upregulation of NF-κB signaling and pro-inflammatory cytokine expression as well as LC3B protein downregulation. Treatment with the autophagy activator Torin-1 ameliorated the pro-inflammatory effects of METTL14 silencing. Furthermore, METTL14 knockdown significantly reduced the expression of ATG5. ATG5 overexpression could nullify the pro-inflammatory effect of METTL14 knockdown in TNF-α-stimulated Caco-2 cells. Mechanistically, METTL14 knockdown promoted ATG5 mRNA degradation, and luciferase analysis identified ATG5 as a target of m6A modification by METTL14. Taken together, silencing METTL14 promoted inflammation in Caco-2 cells via the downregulation of ATG5. Our findings revealed the importance of the m6A modification in colonic inflammation and autophagy, indicating that targeting METTL14 might be a potential therapeutic strategy for anti-inflammatory treatment in UC.

Geraniin Alleviates Inflammation in Caco-2 Cells and Dextran Sulfate Sodium-Induced Colitis Mice by Targeting IL-1β.

IL-1β is an important cytokine implicated in the progression of inflammatory bowel disease (IBD) and intestinal barrier dysfunction. The polyphenolic compound, geraniin, possesses bioactive properties, such as antitumor, antioxidant, anti-inflammatory, antihypertensive, and antiviral activities; however, its IL-1β-targeted anticolitis activity remains unclear. Here, we evaluated the inhibitory effect of geraniin in IL-1β-stimulated Caco-2 cells and a dextran sulfate sodium (DSS)-induced colitis mouse model. Geraniin blocked the interaction between IL-1β and IL-1R by directly binding to IL-1β and inhibited the IL-1β activity. It suppressed IL-1β-induced intestinal tight junction damage in human Caco-2 cells by inhibiting IL-1β-mediated MAPK, NF-kB, and MLC activation. Moreover, geraniin administration effectively reduced colitis symptoms and attenuated intestinal barrier injury in mice by suppressing elevated intestinal permeability and restoring tight junction protein expression through the inhibition of MAPK, NF-kB, and MLC activation. Thus, geraniin exhibits anti-IL-1β activity and anticolitis effect by hindering the IL-1β and IL-1R interaction and may be a promising therapeutic anti-IL-1β agent for IBD treatment.

Gallic acid attenuates LPS-induced inflammation in Caco-2 cells by suppressing the activation of the NF-κB/MAPK signaling pathway.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease characterized by intestinal barrier dysfunction, inflammatory synergistic effects and excessive tissue injury. Gallic acid (GA) is renowned for its remarkable biological activity, encompassing anti-inflammatory and antioxidant properties. However, the underlying mechanisms by which GA protects against intestinal inflammation have not been fully elucidated. The aim of this study is to investigate the effect of GA on the inflammation of a lipopolysaccharide (LPS)-stimulated human colon carcinoma cell line (Caco-2) and on the intestinal barrier dysfunction, and explore the underlying molecular mechanism involved. Our findings demonstrate that 5 μg/mL GA restores the downregulation of the mRNA and protein levels of Claudin-1, Occludin, and ZO-1 and decreases the expressions of inflammatory factors such as IL-6, IL-1β and TNF-α induced by LPS. In addition, GA exhibits a protective effect by reducing the LPS-enhanced early and late apoptotic ratios, downregulating the mRNA levels of pro-apoptotic factors ( Bax, Bad, Caspase-3, Caspase-8, and Caspase-9), and upregulating the mRNA levels of anti-apoptotic factor Bcl-2 in Caco-2 cells. GA also reduces the levels of reactive oxygen species increased by LPS and restores the activity of antioxidant enzymes, namely, superoxide dismutase and catalase, as well as the level of glutathione. More importantly, GA exerts its anti-inflammatory effects by inhibiting the LPS-induced phosphorylation of key signaling molecules in the NF-κB/MAPK pathway, including p65, IκB-α, p38, JNK, and ERK, in Caco-2 cells. Overall, our findings show that GA increases the expressions of tight junction proteins, reduces cell apoptosis, relieves oxidative stress and suppresses the activation of the NF-κB/MAPK pathway to reduce LPS-induced intestinal inflammation in Caco-2 cells, indicating that GA has potential as a therapeutic agent for intestinal inflammation.

Combined Lycium barbarum Polysaccharides with Plasmon-Activated Water Affect IFN-γ/TNF-α Induced Inflammation in Caco-2 Cells.

The effects of Lycium barbarum polysaccharides (LBP) and plasmon-activated water (PAW) against IFN-γ/TNF-α induced inflammation in human colon Caco-2 cells were investigated. Cells were divided into the control, induction, LBP treatment (100-500 μg/mL), and combination groups with PAW. Inflammation was induced 24 h with 10 ng/mL IFN-γ when cell confluency reached >90%, and various doses of LBP with or without PAW were treated for 3 h, and subsequently 50 ng/mL TNF-α was added for another 24 h to provoke inflammation. Combination of LBP with PAW significantly decreased the secretion of IL-6 and IL-8. Cyclooxygenase-2 and inducible NO synthase expression was attenuated in all LBP-treated groups with or without PAW. NLRP3 inflammasome and related protein PYCARD expression were inhibited by LBP at the highest dose (500 μg/mL). All doses of LBP alone significantly decreased p-ERK expression, but combination with PAW increased p-ERK expression compared to those without PAW. Additionally, 250 and 500 μg/mL of LBP with or without PAW inhibited procaspase-3/caspase-3 expression. Therefore, LBP possesses anti-inflammation and anti-apoptosis by inhibiting the secretion of inflammatory cytokines and the expression of NLRP3 inflammasome-related protein. The combination with PAW exerts additive or synergistic effect on anti-inflammation.

Oxidized lipids from heated olive oil induce intestinal inflammation in Caco-2 cells: An oxidomics-based study

Oxidized lipids from heated olive oil induce intestinal inflammation in Caco-2 cells: An oxidomics-based study

TGF-β receptor I inhibitor may restrict the induction of EMT in inflamed intestinal epithelial cells.

Despite the extensive body of research, understanding the exact molecular mechanisms governing inflammatory bowel diseases (IBDs) still demands further investigation. Transforming growth factor-β1 (TGF-β1) signaling possesses a multifacial effect on a broad range of context-dependent cellular responses. However, long-term TGF-β1 activity may trigger epithelial-mesenchymal transition (EMT), followed by fibrosis. This study aimed to determine the role of epithelial TGF-β1 signaling in inflammatory bowel disease (IBD) pathogenesis. The expression of TGF-β1 signaling components and EMT-related and epithelial tight junction markers was examined in IBD patients (n = 60) as well as LPS-induced Caco-2/RAW264.7 co-culture model using quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting, and immunofluorescence staining. Furthermore, the effect of A83-01, as a TGF-β receptor I (TβRI) inhibitor, on the inflamed epithelial cells was evaluated in vitro. To evaluate the cytotoxic effects of the TβRI inhibitor, a cell viability assay was performed by the MTS method. Considering the activation of canonical and non-canonical TGF-β1 signaling pathways in IBD patients, expression results indicated that administering A83-01 in inflamed Caco-2 cells substantially blocked the expression level of TGF-β1, SMAD4, and PI3K and the phosphorylation of p-SMAD2/3, p-AKT, and p-RPS6 as well as prevented downregulation of LncGAS5 and LncCDKN2B. Further analysis revealed that the inhibition of TGF-β1 signaling in inflamed epithelial cells by the small molecule could suppress the EMT-related markers as well as improve the expression of epithelial adherens and tight junctions. Collectively, these findings indicated that the inhibition of the TGF-β1 signaling could suppress the induction of EMT in inflamed epithelial cells as well as exert a protective effect on preserving tight junction integrity. There is a pressing need to determine the exact cellular mechanisms by which TGF-β1 exerts its effect on IBD pathogenesis.

Egg White Protein Ovotransferrin-Derived IRW (Ile-Arg-Trp) Inhibits LPS-Induced Barrier Integrity Dysfunction and Inflammation in Caco-2 Cells.

Tripeptide IRW derived from egg ovotransferrin was initially identified to be an inhibitor of angiotensin-converting enzyme. Later, IRW has been shown to possess various bioactivities, including anti-inflammatory activity and the ability to suppress colitis development. Nevertheless, its role in protecting intestinal barrier integrity has not been reported. This study aims to investigate the effect of IRW on inhibiting intestinal barrier dysfunction and inflammation in lipopolysaccharide (LPS)-treated Caco-2 cells. Pretreatment with IRW could mitigate the LPS-induced reduction of transepithelial electronic resistance values and decrease the paracellular permeation of differentiated Caco-2 cell monolayers. Meanwhile, IRW restored the expression level and cell surface distribution of the tight junction protein occludin. Furthermore, IRW showed LPS-neutralizing activity and could significantly inhibit LPS-induced activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. In conclusion, our study demonstrated the ability of IRW to prevent LPS-induced intestinal barrier dysfunction and prohibit inflammatory responses.

Retraction Note: Adiponectin administration alleviates DSS-induced colonic inflammation in Caco-2 cells and mice.

Retraction Note: Adiponectin administration alleviates DSS-induced colonic inflammation in Caco-2 cells and mice.

Anti-apoptotic effects of high hydrostatic pressure treated cyanidin-3-glucoside and blueberry pectin complexes on lipopolysaccharide-induced inflammation in Caco-2 cells

To investigate whether complexes of cyanidin-3-glucoside (C3G) and blueberry pectin (BP) can exert protective effects on lipopolysaccharide (LPS)-induced Caco-2 inflammatory cells, as well as the influence of high hydrostatic pressure (HHP) processing on the activities of the complexes, for determining their anti-apoptosis in vitro. LPS-induced Caco-2 cells were treated with C3G-BP complexes with or without HHP treatment. Results showed that C3G-BP complexes (100–100 µg/mL) inhibited the depolarization of mitochondria and reduced the production of ROS, as demonstrated by the reduced mRNA expression of IL-1β, TNF-α, and IL-8; increased expression of IL-10; and reduced iNOS, COX-2, Bcl-2, and cleaved caspase-3 levels. These findings reveal that C3G-BP exerts anti-apoptosis effects by inhibiting several mediators and cytokines involved in the inflammatory process. Furthermore, HHP-treated C3G-BP complexes better reduced cell apoptosis than untreated complexes, owing to the high pressure-mediated alterations in the monosaccharide composition of the complexes. This study provides insights for the functional changes of anthocynin-pectin complexes during food processing applications.

Cooking Methods on Extractability and Bioactivity of Phenolic Compounds in Purple Potatoes

Abstract Objectives Purple-fleshed potato is a good dietary source of phenolic compounds, including anthocyanins, flavonols, and chlorogenic acids. The objective of this study is to examine impacts of cooking methods including boiling, steaming and the newly developed vacuum-sealed boiling (VSBoiling), on extractability and bioactivity of phenolic compounds in purple potato (PP). Methods Following cooking, polyphenolic compounds were extracted from raw PP or cooked PP and analyzed for total phenolic content, composition, and free radical scavenging activity. In addition, anti-oxidative and anti-inflammatory effects of extracts were tested in cultured Caco-2 cells. Results Steaming and boiling slightly reduced the extractable chlorogenic acid content, while VSBoiling increased its content. VSBoiling and steaming effectively preserved the radical scavenging activities of PP, while boiling resulted in a significant reduction compared to the extract from raw potatoes. In human colonic epithelial Caco-2 cells, all PP extracts effectively suppressed hydrogen peroxide-induced bursts of intracellular reactive oxygen species, and suppressed tumor necrosis factor-α induced inflammation in Caco-2 cells, while VSBoiling group showed the highest activity. Conclusions The contents and bioactivity of extractable polyphenols are largely retained in PP subjected to different cooking processes. VSBoiling resulted in the highest extractability of phenolic compounds and their biological function among tested cooking methods. Funding Sources USDA-NIFA and Northwest Potato Research Consortium.

Bioactivities of Pseudocereal Fractionated Seed Proteins and Derived Peptides Relevant for Maintaining Human Well-Being.

Food proteins and peptides are able to exert a variety of well-known bioactivities, some of which are related to well-being and disease prevention in humans and animals. Currently, an active trend in research focuses on chronic inflammation and oxidative stress, delineating their major pathogenetic role in age-related diseases and in some forms of cancer. The present study aims to investigate the potential effects of pseudocereal proteins and their derived peptides on chronic inflammation and oxidative stress. After purification and attribution to protein classes according to classic Osborne’s classification, the immune-modulating, antioxidant, and trypsin inhibitor activities of proteins from quinoa (Chenopodium quinoa Willd.), amaranth (Amaranthus retroflexus L.), and buckwheat (Fagopyrum esculentum Moench) seeds have been assessed in vitro. The peptides generated by simulated gastro-intestinal digestion of each fraction have been also investigated for the selected bioactivities. None of the proteins or peptides elicited inflammation in Caco-2 cells; furthermore, all protein fractions showed different degrees of protection of cells from IL-1β-induced inflammation. Immune-modulating and antioxidant activities were, in general, higher for the albumin fraction. Overall, seed proteins can express these bioactivities mainly after hydrolysis. On the contrary, higher trypsin inhibitor activity was expressed by globulins in their intact form. These findings lay the foundations for the exploitation of these pseudocereal seeds as source of anti-inflammatory molecules.

Preventive and Therapeutic Spermidine Treatment Attenuates Acute Colitis in Mice.

Inflammatory bowel disease (IBD) is associated with acute and chronic inflammation of the gastrointestinal tract and has emerged to be a global disease. Spermidine, a natural polyamine, plays a critical role in maintaining cellular homeostasis. Herein, we investigated the impact and mechanism of spermidine on both dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-induced colitis in mice. We found that spermidine exerted protective effects against acute colitis, evidenced by reduced disease activity index (DAI) and colonic inflammation, increased colonic length, and upregulated tight junction proteins in these two colitis models. Importantly, spermidine exerted significant therapeutic and preventive effects against DSS-induced colitis. Pre- and post-treatment with spermidine reduced the expression of proinflammatory cytokines, phosphorylation of (nuclear factor-κB) NF-κB and (mitogen-activated protein kinase) MAPK, and the activation of F4/80 macrophages and T cells in the colon. Furthermore, spermidine upregulated M2 macrophage markers, whereas it downregulated M1 markers in the inflamed colons. In parallel, spermidine reduced M1 pro-inflammatory markers and enhanced M2 anti-inflammatory genes in RAW264.7 cells. These results revealed that spermidine-ameliorated colitis might be through the regulation of M1/M2 macrophage polarization. In addition, spermidine treatment also alleviated LPS/TNF-α-induced inflammation in Caco-2 cells. Taken together, spermidine prevented and reversed colonic inflammation in colitis mice and might be a promising candidate for IBD intervention.

Weissella cibaria Attenuated LPS-Induced Dysfunction of Intestinal Epithelial Barrier in a Caco-2 Cell Monolayer Model.

The dysfunction of the intestinal epithelial barrier contributes to local or systemic infection and inflammation. Some lactic acid bacteria (LAB) strains had been shown to improve the conditions of barrier function and, for this reason, are recognized as probiotics. Weissella cibaria, a species belonging to the LAB group, is known to promote several health benefits. However, the role of W. cibaria in regulating the integrity of the intestinal epithelial barrier has not yet been investigated. In this study, W. cibaria MW01 was isolated from Chinese sauerkraut and was selected based on its functional features, such as gastric juice and bile salt tolerance, besides antagonistic activity against pathogenic bacteria. In a cellular model of the intestinal barrier, it was observed that W. cibaria was able to adhere more efficiently than Lactobacillus rhamnosus GG in Caco-2 cells. Moreover, the LPS-induced inflammation in Caco-2 cells was attenuated by the treatment with W. cibaria MW01, which reduced the synthesis of TNF-α, IL-6, and IL-8. In addition, it was noted that the treatment with W. cibaria MW01 recovered the integrity of the Caco-2 cell monolayer exposed to LPS. Furthermore, W. cibaria MW01 significantly alleviated LPS-induced downregulation of tight junction proteins (TJP) (claudin, occludin, and tight junction protein-1). Mechanistically, W. cibaria MW01 inhibited the translocation of NF-κB to the nucleus and deactivated the MLCK-pMLC pathway during LPS exposure. Thus, W. cibaria MW01, as a potential probiotic, can protect intestinal epithelial barrier function by regulating inflammation and expression of TJP via the NF-κB-mediated MLCK-pMLC pathway.

Biotransformed grape pomace as a potential source of anti-inflammatory polyphenolics: Effects in Caco-2 cells

Grape pomace is rich in polymeric phenolic compounds and glycosides. Enzymatic treatments may change grape pomace’s phenolic composition, producing monomers and aglycones. The aims of this study were to evaluate if tannase-biotransformed grape pomace extracts have improved intestinal anti-inflammatory activity using an in vitro colon model and to analyze significant differences between white grape pomace, and mixed grape pomace varieties, due to the absence of a pomace fermentation process during white wine production. No differences were observed in the cytotoxicity caused by different extracts. All extracts, before and after biotransformation at 100 and 200 μg/mL (dry extract w/v) had comparable efficacy in reducing reactive oxygen species production in Caco-2 cells. After treatment and induction of inflammation using an interleukin 1β (IL-1β) challenge, tannase-treated white grape pomace extract at 200 μg/mL was the most efficient treatment in down-regulating nuclear factor kappa B activation by 40%, compared to control. On the other hand, tannase-treated mixed grape pomace extract significantly decreased prostaglandin E2 production by 81% and interleukin-8 by 61%, being more effective than white grape pomace extract. Overall, both grape pomace extracts after biotransformation were more potent in the amelioration of IL-1β-induced inflammation in Caco-2 cells. White grape pomace extract did not show higher anti-inflammatory activity than mixed grape pomace. In general, the biotransformation improved the anti-inflammatory effect in Caco-2 cells, indicating that the application of a bioprocess in grape residues may contribute to the development of new ingredients and nutraceuticals with anti-inflammatory potential.

Simulated gastrointestinal digests of corn protein hydrolysate alleviate inflammation in caco-2 cells and a mouse model of colitis.

Inflammatory bowel disease, a typical chronic inflammatory disease of the gastrointestinal tract, make up a growing share of the global disease burden. This study firstly evaluated the anti-inflammatory effects of corn protein hydrolysate (CPH) using a cell model of tumor cell necrosis factor-α (TNF-α)-induced inflammation and a mouse model of colitis induced by dextran sodium sulfate. CPH digests significantly inhibited the expression of cyclooxygenase-2 and inducible nitric oxide synthase, and reduced the secretion of interleukin-8 in TNF-α-induced inflammation in Caco-2 cells. In mice, CPH digests significantly improved the body weight loss, clinical scores, shortening of the colon and histological symptoms, and decreased the myeloperoxidase activity, and down regulated the expression of TNF-α, and interleukin-6 in the colon. The above results indicate that the CPH can potentially be used as a health food/nutraceutical for the treatment/management of intestinal inflammation.

Red-Osier Dogwood Extracts Prevent Inflammatory Responses in Caco-2 Cells and a Caco-2 BBe1/EA.hy926 Cell Co-Culture Model.

Red-osier dogwood extracts (RDE) contain high levels of phenolic compounds which have been recognized as natural antioxidants. In this study, the potential of RDE to prevent cardiovascular diseases (CVDs) was evaluated using Caco-2 cells and a co-culture model of Caco-2 BBe1/EA.hy926 cells in Transwell® plates. The results showed that RDE supplementation significantly prevented interleukin-8 (IL-8) production and suppressed the gene expression of IL-8, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and cyclooxygenase 2 (COX-2) in the TNF-α inflamed Caco-2 cells. Meanwhile, the polyphenols (quercetin-3-glucoside, quercetin-glucuronide, rutin, quercetin-3-O-malonylglucoside, and kaempferol-glucoside) in the RDE were validated to be absorbed by Caco-2 BBe1 cells and transported to the basal chamber where EA.hy926 cells were located during 12 h incubation. The transported polyphenols were able to prevent IL-8 production and suppress the gene expression of proinflammatory mediators (TNF-α, ICAM-1, VCAM-1, and COX-2) in the TNF-α or oxidized low-density lipoprotein (ox-LDL) treated EA.hy926 cells. These novel findings demonstrated that phenolic compounds in RDE can be transported to the cardiovascular system by intestinal absorption and mitigate the inflammatory responses of vascular endothelial cells, indicating that RDE could be a natural resource of polyphenols to prevent inflammation cytokine or oxidized lipid-induced CVDs.

Surface-layer protein from Lactobacillus acidophilus NCFM attenuates tumor necrosis factor-α-induced intestinal barrier dysfunction and inflammation

Lactobacillus acidophilus NCFM, a probiotic generally regarded as safe, carries a proteinaceous surface (S) layer, composed of numerous identical subunits (surface layer protein, Slp). S-layer proteins have been confirmed to possess multiple biological properties, but their role in maintaining the intestinal epithelial barrier is not fully known. We investigated the effects of Slp on tumor necrosis factor (TNF)-α-elicited intestinal barrier dysfunction and explored the underlying molecular mechanism. TNF-α administration markedly induced intestinal epithelial injury and inflammation in Caco-2 cells. Preincubation of Caco-2 cells with Slp at concentrations ranging from 50 to 100 μg/mL for 6 h improved intestinal epithelial cell integrity and permeability, restored ZO-1 and Occludin protein expressions (P < 0.05) and reduced the secretion of interleukin 8 by a maximum of 47.8%. Furthermore, the addition of Slp to Caco-2 cell monolayers attenuated cell apoptosis and inhibited nuclear factor-κB (NF-κB) p65 nucleus translocation by suppressing the activation of NF-κB. Collectively, the ability of Slp to attenuate dysfunction of the intestinal epithelial barrier stimulated by TNF-α and to exert anti-inflammatory effects supports its potential use in the development of functional foods and in the prevention of inflammatory bowel diseases.

Chlorogenic acid isomers directly interact with Keap 1-Nrf2 signaling in Caco-2 cells

Chlorogenic acid (CGA) exists as multiple isomers (e.g., 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) in foods such as coffee beverages, fruits and vegetables. This study aimed to investigate relative activities of these six different CGA isomers to modify redox biology in inflamed Caco-2 cells that involved Nrf2 signaling. Caco-2 cells were pre-treated with individual CGA isomers to assess the relative effectiveness to mitigate oxidative stress. Isomer-specific capacity of different CGA isomers for direct free radical scavenging activity and potential endogenous control of oxidative stress were determined using chemical assays and cell-based experiments, respectively. Molecular dynamics simulations of the CGA and Keap1-Nrf2 complex were performed to predict CGA structure-specific interactions. Results demonstrated that dicaffeoylquinic acid (diCQA including 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) isomers had greater (p < 0.05) affinity to ameliorate oxidative stress through direct free radical scavenging activity. This observation corresponded to greater (p < 0.05) capacity to activate Nrf2 signaling compared to caffeoylquinic acid (CQA including 3-CQA, 4-CQA, and 5-CQA) isomers in inflamed differentiated Caco-2 cells. Simulations revealed that differences between the ability of CQA and diCQA to interact with the Keap1-Nrf2 complex may be due to differences in relative orientation within this complex. The observed CGA isomer-specific affinity for CQA to activate Nrf2 signaling was confirmed by nuclear translocation of Nrf2 induced by CGA and greater (p < 0.05) upregulation of genes related to Nrf2 expression.

Therapeutic effects of kefir grain Lactobacillus-derived extracellular vesicles in mice with 2,4,6-trinitrobenzene sulfonic acid-induced inflammatory bowel disease

Kefir is a fermented product from yeast and lactic acid bacteria, and has been associated with various health benefits including relieving inflammatory bowel disease. Recently, it has been shown that gram-positive bacteria produce extracellular vesicles (EV). The EV could be appearing as potentially important mediators of cell to cell interaction. In this study, we explored the role of kefir grain Lactobacillus-derived EV in modulating inflammation responses via alleviating the production of inflammatory cytokines in tumor necrosis factor-α (TNF-α)-induced inflammation in Caco-2 cells and the 2,4,6-trinitrobenzene sulfonic acid-induced inflammatory bowel disease mouse model. Kefir-derived Lactobacillus EV were isolated by ultracentrifugation of the culture medium of 3 different kefir-derived strains (i.e., Lactobacillus kefir, Lactobacillus kefiranofaciens, and Lactobacillus kefirgranum). Nanoparticle tracking analysis showed that the size of isolated kefir-derived Lactobacillus EV was within 80 to 400 nm, and kefir-derived Lactobacillus EV uptake into recipient Caco-2 cells was confirmed by fluorescence labeling. Treatment of each kefir-derived Lactobacillus EV onto TNF-α-stimulated Caco-2 cells significantly reduced the level of both mRNA expression and secretion of IL-8, and Western blot analysis revealed that such an effect was related to inhibition of TNF-α signaling mediated by reducing the phosphorylation of p65, a subunit of NF-kB. Subsequent administration of kefir-derived Lactobacillus EV into inflammatory bowel disease-induced mice significantly alleviated the body weight loss and rectal bleeding, and enhanced stool consistency. Histological examination showed that kefir-derived Lactobacillus EV substantially reduced the infiltration of transmural leukocytes and loss of goblet cells within the colon, and the serum level of myeloperoxidase was significantly lower in the EV-treated group than control group. Our study demonstrates that kefir-derived Lactobacillus EV can be potentially used for developing innovative strategies for alleviating inflammatory bowel disease.