Tandem repeats structure of gel-forming mucin domains could be revealed by SMRT sequencing data

Identification and Validation of Cyclic Peptides with Mucin-Selective, Location-Specific Binding in the Gastrointestinal Tract

Oral drug delivery is a widely preferred method of drug administration due to its ease of use and convenience for patients. Localization of drug release in the gastrointestinal (GI) tract is important to treat localized diseases and maximize drug absorption. However, achieving drug localization in the dynamic GI tract is challenging. To address this challenge, we leveraged the geographic diversity of the GI tract by targeting its mucus layers, which coat the epithelial surfaces. These layers, composed of mucin glycoproteins, are synthesized with unique chemical compositions and expressed in different regions, making them ideal targets for drug localization. In this article, we identify cyclic peptides that bind selectively to MUC2 (in the intestines) and MUC5AC (in the stomach), serving as targeting ligands to these regions of the GI tract. We demonstrate the effectiveness of these peptides through in vitro, ex vivo, and in vivo experiments, showing that incorporating these targeting ligands can increase binding and selectivity 2-fold to the desired regions, thus potentially overcoming challenges with localizing drug distribution in oral delivery. These results indicate that cyclic peptides can be used to localize drug cargoes at certain sites in the body compared to free drugs.

Identification and Validation of Small Molecules with Mucin-Selective Regiospecific Binding in the Gastrointestinal Tract

Oral drug delivery is a widely used method of drug administration; however, achieving localized drug release at specific regions of the gastrointestinal (GI) tract is generally accomplished by using broad environmental differences. The GI tract is a complex system with regional differences in composition, such as selective expression of mucin glycoproteins in different organs. Here, we identify small molecule ligands that can selectively bind to the different mucins to localize drug delivery to the small intestine and stomach. We demonstrate up to a 10-fold increase in particle binding to these organs and up to a 4-fold increase in selectivity compared to chitosan. Additionally, we observe up to a 9-fold increase in budesonide concentration in the small intestine and a 25-fold increase in tetracycline concentration in the stomach. These results show that we have developed a versatile platform capable of sequestering a variety of drugs in certain GI tract organs.

Intestinal mucus barrier: A potential therapeutic target for IBD

Intestinal mucus, a viscoelastic medium with mucin2 (MUC2) as its main component, covers the surface of intestinal epithelial cells and protects the intestine from invasion, forming the first barrier of the intestinal tract. Unlike the small intestine, where the mucus layer is a single layer, the colonic mucus layer can be divided into a sterile inner layer and an outer layer with bacterial colonization. Many of the substances in the mucus layer have beneficial effects on the intestinal epithelium, but the mucus layer is often affected by a variety of factors, mainly microbiological, dietary, and immunological. Inflammatory bowel disease (IBD) is a disease of increasing morbidity worldwide, with a complex etiology and a high relapse rate. In recent years, the mucus barrier in IBD has received increasing attention and is considered a key factor in the pathogenesis of IBD. Loss of goblet cells (GCs) and changes in the composition and properties of the mucus layer material are commonly found in the colon of IBD patients. Damage to the mucus layer may make it easier for microorganisms to access the intestinal epithelium and cause inflammation. There are currently a number of herbs and other therapies that can be used to treat IBD and repair the damaged mucus barrier. This review highlights the important role of the mucus layer in IBD and the therapies that target the mucus layer in IBD.

Rapid building block-economic synthesis of long, multi-O-GalNAcylated MUC5AC tandem repeat peptides

The study of mucin function requires access to highly O-glycosylated peptides with multiple tandem repeats. Solid-phase synthesis would be a suitable method, however, the central problem in the synthesis of mucin glycopeptides is the need to use precious and potentially vulnerable glycoamino acid building blocks in excess. In this article, we report the development of a method based on SPPS and native chemical ligation/desulfurization chemistry that allows the rapid, reliable, and glyco-economical synthesis of long multi-O-GalNAcylated peptides. To facilitate access to the glycosyl donor required for the preparation of Fmoc-Ser/Thr(αAc3GalNAc)-OH we used an easily scalable azidophenylselenylation of galactal instead of azidonitration. The problem of low yield when coupling glycoamino acids in small excess was solved by carrying out the reactions in 2-MeTHF instead of DMF and using DIC/Oxyma. Remarkably, quantitative coupling was achieved within 10 minutes using only 1.5 equivalents of glycoamino acid. The method does not require (microwave) heating, thus avoiding side reactions such as acetyl transfer to the N-terminal amino acid. This method also improved the difficult coupling of glycoamino acid to the hydrazine-resin and furnished peptides carrying 10 GalNAc units in high purities (>95%) of crude products. Combined with a one-pot method involving native chemical ligation at a glycoamino acid junction and superfast desulfurization, the method yielded highly pure MUC5AC glycopeptides comprising 10 octapeptide tandem repeats with 20 α-O-linked GalNAc residues within a week.