Mechanisms of interactions in pattern-recognition of common glycostructures across pectin-derived heteropolysaccharides by Toll-like receptor 4

Citrus pectins impact the function of chicken macrophages

The restrictions on excessive use of antimicrobials in the poultry industry have led to the search for alternative strategies including nutritional interventions to enhance gut health with the ultimate aim to prevent gut infections. Pectins as prebiotics have shown beneficial effects on gut health in humans and mice by improving the gut barrier function, altering the gut microbiota, and by modulating the gut immune response. However, little is known about immunomodulatory properties of pectins in chickens. The present in vitro study assessed the effect of three pectins (SPE6, SPE7, SPE8) differing in methyl esterification, on responsiveness of the chicken macrophage cell line HD11 cells and primary monocyte derived macrophage from the blood, through interaction with chicken TLRs. All three pectins increased gene expression of iNOS and IL10 in chicken macrophages. Differences in immunomodulatory activity between the three pectins were observed in other assays. The low methoxyl pectin (SPE8) interacted with TLR4 leading to the production of NO, but also to increased phagocytosis of E. coli, while high methoxyl pectins SPE6 and SPE7 did not activate TLR4. All three pectins were able to attenuate PAM3CSK4 induced activation of chicken macrophages as measured by decreased NO production and phagocytosis. Additional studies using ITC and flow cytometry suggest that the inhibiting properties of pectins (SPE6, SPE7) on macrophages are due to pectins occupying TLR2 and blocking PAM3CSK4 to activate chicken macrophages, whereas SPE8 actually binds to the TLR2 ligand and that way attenuates the PAM3CSK4 induced activation. Based on these immunomodulatory properties observed in this study, these pectins may in the future be suitable as feed additive for the treatment and prevention of inflammatory disorders in poultry.

Covalent Modification of Selenium in Polysaccharide Enhances Immunoregulation Activity via the TLR4-Mediated MAPK/NF-κB Signaling Pathway

Selenium (Se) is a crucial trace element that demonstrates significant immunomodulatory effects, which are attributed to the variability in its valence states and metabolic pathways. To investigate the Se-related immunoregulatory effects, locust bean gum (LBG), a typical galactomannan, was selenized by employing deep eutectic solvents (DESs) as high-efficiency solvents to obtain Se-covalent modified LBG (SeLBGs) with similar molecular mass and different Se contents (SeLBGL, 1049.57 and SeLBGH, 4926.54 μg/g). After introducing selenite into LBG, SeLBGs display greater immunomodulatory activities by activating MAPKs and NF-κB signaling pathways compared with LBG and Se compounds (Se-Met, Na2SeO3, and SeNPs) at the same Se equivalent, which are confirmed by their higher cell viability, phagocytic activity, secretion of cytokines, and protein expression. In addition, molecular docking and molecular dynamics suggest that SeLBG has the potential to induce dimerization of subunits and activate toll-like receptors (TLRs). By employing the specific receptor inhibitors strategy, it is confirmed that the combination of Se and LBG enhances TLR2/4 recognition according to the results of cytokine secretion and MAPKs/NF-κB pathway-related protein expression. These findings underscore the role of Se in pattern receptor recognition and the potential of Se-enriched ingredients in various functions.

From Structure to Function: How Prebiotic Diversity Shapes Gut Integrity and Immune Balance

The microbiota stability, diversity, and composition are pillars for an efficient and beneficial symbiotic relationship between its host and itself. Microbial dysbiosis, a condition where a homeostatic bacterial community is disturbed by acute or chronic events, is a predisposition for many diseases, including local and systemic inflammation that leads to metabolic syndrome, diabetes, and some types of cancers. Classical dysbiosis occurs in the large intestine. During this period, pathogenic strains can multiply, taking advantage of the compromised environment. This overgrowth triggers an exaggerated inflammatory response from the human immune system due to the weakened integrity of the intestinal barrier. Such inflammation can also directly influence higher polyp formation and/or tumorigenesis. Prebiotics can be instrumental in preventing or correcting dysbiosis. Prebiotics are molecules capable of serving as substrates for fermentation processes by gut microorganisms. This can promote returning the intestinal environment to homeostasis. Effective prebiotics are generally specific oligo- and polysaccharides, such as FOS or inulin. However, the direct effects of prebiotics on intestinal epithelial and immune cells must also be taken into consideration. This interaction happens with diverse prebiotic nondigestible carbohydrates, and they can inhibit or decrease the inflammatory response. The present work aims to elucidate and describe the different types of prebiotics, their influence, and their functionalities for health, primarily focusing on their ability to reduce and control inflammation in the intestinal epithelial barrier, gut, and systemic environments.

Intestinal lymphatic transport of Smilax china L. pectic polysaccharide via Peyer's patches and its uptake and transport mechanisms in mononuclear phagocytes

Recently, the intestinal lymphatic transport based on Peyer's patches (PPs) is emerging as a promising absorption pathway for natural polysaccharides. Herein, the aim of this study is to investigate the PP-based oral absorption of a pectic polysaccharide from Smilax china L. (SCLP), as well as its uptake and transport mechanisms in related immune cells. Taking advantages of the traceability of fluorescently labeled SCLP, we confirmed that SCLP could be absorbed into PPs and captured by their mononuclear phagocytes (dendritic cells and macrophages) following oral administration. Subsequently, the systematic in vitro study suggested that the endocytic mechanisms of SCLP by model mononuclear phagocytes (BMDCs and RAW264.7 cells) mainly involved caveolae-mediated endocytosis, macropinocytosis and phagocytosis. More importantly, SCLP directly binds and interacts with toll-like receptor 2 (TLR2) and galectin 3 (Gal-3) receptor, and was taken up by mononuclear phagocytes in receptor-mediated manner. After internalization, SCLP was intracellularly transported primarily through endolysosomal pathway and ultimately localized in lysosomes. In summary, this work reveals novel information and perspectives about the in vivo fate of SCLP, which will contribute to further research and utilization of SCLP and other pectic polysaccharides.

Potential structure-function relationships of pectic polysaccharides from quinoa microgreens: Impact of various esterification degrees

Pectic polysaccharides are one of the most vital functional ingredients in quinoa microgreens, which exhibit numerous health-promoting benefits. Nevertheless, the detailed information about the structure-function relationships of pectic polysaccharides from quinoa microgreens (QMP) remains unknown, thereby largely restricting their applications as functional foods or fortified ingredients. Therefore, to unveil the possible structure-function relationships of QMP, the mild alkali de-esterification was utilized to modify QMP, and then the correlations of esterification degrees of native and modified QMPs to their biological functions were systematically investigated. The results showed that the modified QMPs with different esterification degrees were successfully prepared by the mild alkali treatment, and the primary chemical structure (e.g., compositional monosaccharides and glycosidic linkages) of the native QMP was overall stable after the de-esterified modification. Furthermore, the results revealed that the antioxidant capacity, antiglycation effect, prebiotic potential, and immunostimulatory activity of the native QMP were negatively correlated to its esterification degree. In addition, both native and modified QMPs exerted immunostimulatory effects through activating the TLR4/NF-κB signaling pathway. These results are conducive to unveiling the precise structure-function relationships of QMP, and can also promote its applications as functional foods or fortified ingredients.

A glucuronogalactomannan isolated from Tetrastigma hemsleyanum Diels et Gilg: Structure and immunomodulatory activity

A novel acidic glucuronogalactomannan (STHP-5) was isolated from the aboveground part of Tetrastigma hemsleyanum Diels et Gilg with a molecular weight of 3.225 × 105 kDa. Analysis of chain conformation showed STHP-5 was approximately a random coil chain. STHP-5 was composed mainly of galactose, mannose, and glucuronic acid. Linkages of glycosides were measured via methylation analysis and verified by NMR. In vitro, STHP-5 induced the production of nitric oxide (NO) and secretion of IL-6, MCP-1, and TNF-α in RAW264.7 cells, indicating STHP-5 had stimulatory activity on macrophages. STHP-5 was proven to function as a TLR4 agonist by inducing the secretion of secreted embryonic alkaline phosphatase (SEAP) in HEK-Blue™-hTLR4 cells. The TLR4 activation capacity was quantitatively measured via EC50, and it showed purified polysaccharides had stronger effects (lower EC50) on activating TLR4 compared with crude polysaccharides. In conclusion, our findings suggest STHP-5 may be a novel immunomodulator.

Dietary fiber pectin: challenges and potential anti-inflammatory benefits for preterms and newborns

Pectins, a class of dietary fibers abundant in vegetables and fruits, have drawn considerable interest due to their potential anti-inflammatory properties. Numerous studies have indicated that incorporating pectins into infant formula could be a safe strategy for alleviating infant regurgitation and diarrhea. Moreover, pectins have been shown to modulate cytokine production, macrophage activity, and NF-kB expression, all contributing to their anti-inflammatory effects. Despite this promising evidence, the exact mechanisms through which pectins exert these functions and how their structural characteristics influence these processes remain largely unexplored. This knowledge is particularly significant in the context of gut inflammation in developing preterm babies, a critical aspect of necrotizing enterocolitis (NEC), and in children and adults dealing with inflammatory bowel disease (IBD). Our mini review aims to provide an up-to-date compilation of relevant research on the effects of pectin on gut immune responses, specifically focusing on preterms and newborns. By shedding light on the underlying mechanisms and implications of pectin-mediated anti-inflammatory properties, this review seeks to advance our knowledge in this area and pave the way for future research and potential therapeutic interventions.