Inhibition of N-glycosylation by glucosamine hydrochloride inhibits TGF-ß1-induced LOXL2 secretion.

Kidney fibrosis is closely associated with the progression of chronic kidney disease (CKD). Furthermore, copper-containing secretory amine oxidases, such as lysyl oxidase (LOX) and LOX-like 1-4 (LOXL1-4), play pivotal roles in the regulation of extracellular components and facilitate fibrosis. In this study, we investigated the regulation of LOX enzymes in human tubular epithelial HK2 cells to help clarify the role of LOX enzymes in kidney fibrosis. Among 5 LOX enzymes, LOXL2 expression is abundantly expressed in HK2 cells. LOX enzymes inhibitor, ß-aminopropionitrile, suppressed transforming growth factor-ß1 (TGF-ß1)-promoted epithelial-to-mesenchymal transition processes in HK2 cells, indicating that LOX enzymes are involved in TGF-ß1-mediated fibrotic processes. Recent studies suggest that LOX enzymes are secreted into the extracellular spaces by exosomes and promote fibrotic processes. Similar to the previous reports, we observed that exosomes secreted from HK2 cells carry LOXL2 into the extracellular spaces. Furthermore, we determined that N-glycosylation on the asparagine residues plays a key role in LOXL2 secretion. Amino acid mutations in three asparagine residues, which can be glycosylated, suppressed the secretion of mutated LOXL2. Moreover, N-acetylglucosaminyltransferase 5, an enzyme used for the biosynthesis of ß1,6N-acetylglucosamine-branched N-glycans, participated in LOXL2 secretion, and the N-glycosylation inhibitor, glucosamine hydrochloride (GS), inhibited TGF-ß1-mediated LOXL2 secretion and fibrotic processes. Overall, TGF-ß1 promotes LOXL2 secretion and may participate in kidney fibrosis. Our results provide novel insight into the antifibrotic properties of GS that contribute to the inhibition of CKD progression.

Isostearyl Mixed Anhydrides for the Preparation of N-Methylated Peptides Using C-Terminally Unprotected N-Methylamino Acids.

Sustainable and efficient manufacturing methods for N-methylated peptides remain underexplored despite growing interest in therapeutic N-methylated peptides within the pharmaceutical industry. A methodology for the coupling of C-terminally unprotected N-methylamino acids mediated by an isostearic acid halide (ISTAX) and silylating reagent has been developed. This approach allows for the coupling of a wide variety of amino acids and peptides in high yields under mild conditions without the need for a C-terminal deprotection step in the process of C-terminal elongation. These advantages make this a useful synthetic method for the production of peptide therapeutics and diagnostics containing N-methylamino acids.

Organozinc-Mediated Direct C-C Bond Formation via C-N Bond Cleavage of Ammonium Salts.

We report a direct cross-coupling reaction between diarylzinc (Ar2 Zn) and aryltrimethylammonium salts (ArNMe3+ ⋅- OTf) in the presence of LiCl, via C-N bond cleavage. The reaction takes place smoothly upon heating in THF without any external catalyst, enabling an efficient and chemoselective formation of biaryl products. Mechanistic studies indicate that the reaction proceeds through a single electron transfer route.