An UPLC-MS/MS method for targeted analysis of microbial and host tryptophan metabolism after administration of polysaccharides from Atractylodes macrocephala Koidz. in ulcerative colitis mice.

Botanic polysaccharides can be metabolized by gut microbiota into short-chain fatty acids (SCFAs) to exert extensive bioactivities, yet targeted analysis of the effect of botanic polysaccharides on other gut microbial metabolites is scarcely seen. Tryptophan metabolites such as indole and indole derivatives play import roles in health and disease development. Using polysaccharides from Atractylodes macrocephala Koidz. (AMP) in treating ulcerative colitis as the example, we checked the effects of AMP on tryptophan metabolites. After examination of pharmacological effects of AMP, we established an ultra-performance liquid chromatography coupled with mass spectrometry/mass spectrometry (UPLC-MS/MS) method to simultaneously determinate the levels of 30 tryptophan metabolites and used the method to determine the levels of these metabolites in feces and plasma. The detection results showed that 12 metabolites in feces can be detected, and 17 metabolites can be detected in plasma samples. In addition, we found out that total levels of aryl hydrocarbon receptor ligands were decreased in colitis model whereas AMP treatment can increase the levels of total ligands in both feces and plasma. The results indicated that the therapeutical effect of AMP on colitis was associated with modulation of fecal and host tryptophan metabolism. This study provides new insight into the molecular mechanisms of polysaccharides that the beneficial effects of polysaccharides can be achieved by modulating microbial tryptophan metabolism in addition to SCFAs.

Stapling of short cell-penetrating peptides for enhanced tumor cell-and-tissue dual-penetration.

Effective delivery of therapeutics to tumors is generally hampered by the limited penetration of biological barriers imposed by the tumor microenvironment. Despite the broad applications of cell-penetrating peptides (CPPs) for intracellular delivery of therapeutics across membrane bilayers, the discovery of novel CPPs with enhanced tumor tissue permeability remains largely unexplored. Herein, we identified two short stapled CPPs with aromatic cross-links that confer superior dual-penetration in tumor cells and tissues over their linear counterparts. This work may benefit the future applications of constrained CPPs as powerful molecular transporters to access deeper tumor tissues.

Rational Design of a Dual-Targeting Natural Toxin-Like Bicyclic Peptide for Selective Bioenergetic Blockage in Cancer Cells.

Stapled α-helical peptides emerge as one of the attractive peptidomimetics which can efficiently penetrate the cell membrane to access intracellular targets. However, the incorporation of a highly lipophilic cross-link may lead to nonspecific membrane toxicity in certain cases. Here, we report a new class of thioether-tethered bicyclic α-helical peptide to mimic the highly constrained loop-helix structure of natural toxins with the dual-targeting ability for both cell-surface receptors and intracellular targets. The thioether cross-links are introduced to replace the redox-sensitive disulfide bonds in natural toxins via a photoinduced thiol-yne reaction followed by macrolactamization. As a proof of concept, αVß3 integrin targeting ligand was grafted into one of the macrocycles in the bicyclic scaffold, while a mitochondria-targeting proapoptotic motif was introduced into the other macrocycle stabilized by an i, i + 7 alkyl thioether cross-link to recapitulate its α-helical conformation. The obtained dual-targeting bicyclic α-helical BIRK peptides showed highly stable α-helical conformation in the presence of denaturants or under high temperature. Notably, BIRK peptides could induce selective cell death in αVß3 integrin-positive B16F10 cells by interfering with the bioenergetic functions of mitochondria. This work provides a new avenue to design and stabilize α-helical peptides in a highly constrained bicyclic loop-helix scaffold with dual functionality.