Pharmacophore-based discovery of 2-(phenylamino)aceto-hydrazides as potent eosinophil peroxidase (EPO) inhibitors

IL-10+ regulatory B cells mitigate atopic dermatitis by suppressing eosinophil activation

Atopic dermatitis (AD) presents significant therapeutic challenges due to its poorly understood etiology. Eosinophilia, a hallmark of allergic inflammation, is implicated in AD pathogenesis. Interleukin-10 (IL-10)-producing regulatory B (Breg) cells exhibit potent anti-inflammatory effects. However, their role in controlling AD-related eosinophilia is not well understood. To investigate the impact of eosinophils on AD, we employed IL-5Rα-deficient (Il5ra-/-) mice, which lack functional eosinophils. Induction of AD in these mice resulted in attenuated disease symptoms, underscoring the critical role of eosinophils in AD development. Additionally, the adoptive transfer of purified Breg cells into mice with AD significantly alleviated disease severity. Mechanistic studies revealed that IL-10 produced by Breg cells directly inhibits eosinophil activation and infiltration into the skin. In vitro experiments further confirmed that Breg cells inhibited eosinophil peroxidase secretion in an IL-10-dependent manner. Our collective findings demonstrate that IL-10 from Breg cells alleviates AD by suppressing eosinophil activation and tissue infiltration. This study elucidates a novel regulatory mechanism of Breg cells, providing a foundation for future Breg-mediated therapeutic strategies for AD.

Peroxidasin Inhibition by Phloroglucinol and Other Peroxidase Inhibitors

Human peroxidasin (PXDN) is a ubiquitous peroxidase enzyme expressed in most tissues in the body. PXDN represents an interesting therapeutic target for inhibition, as it plays a role in numerous pathologies, including cardiovascular disease, cancer and fibrosis. Like other peroxidases, PXDN generates hypohalous acids and free radical species, thereby facilitating oxidative modifications of numerous biomolecules. We have studied the inhibition of PXDN halogenation and peroxidase activity by phloroglucinol and 14 other peroxidase inhibitors. Although a number of compounds on their own potently inhibited PXDN halogenation activity, only five were effective in the presence of a peroxidase substrate with IC50 values in the low μM range. Using sequential stopped-flow spectrophotometry, we examined the mechanisms of inhibition for several compounds. Phloroglucinol was the most potent inhibitor with a nanomolar IC50 for purified PXDN and IC50 values of 0.95 μM and 1.6 μM for the inhibition of hypobromous acid (HOBr)-mediated collagen IV cross-linking in a decellularized extracellular matrix and a cell culture model. Other compounds were less effective in these models. Most interestingly, phloroglucinol was identified to irreversibly inhibit PXDN, either by mechanism-based inhibition or tight binding. Our work has highlighted phloroglucinol as a promising lead compound for the design of highly specific PXDN inhibitors and the assays used in this study provide a suitable approach for high-throughput screening of PXDN inhibitors.

Direct conversion of amino acids to oxetanol bioisosteres via photoredox catalysis

Carboxylic acids are an important structural feature in many drugs, but are associated with a number of unfavorable pharmacological properties. To address this problem, carboxylic acids can be replaced with bioisosteric mimics that interact similarly with biological targets but avoid these liabilities. Recently, 3-oxetanols have been identified as useful carboxylic acid bioisosteres that maintain similar hydrogen-bonding capacity while decreasing acidity and increasing lipophilicity. However, the installation of 3-oxetanols generally requires multistep de novo synthesis, presenting an obstacle to investigation of these promising bioisosteres. Herein, we report a new synthetic approach involving direct conversion of carboxylic acids to 3-oxetanols using a photoredox-catalyzed decarboxylative addition to 3-oxetanone. Two versions of the transformation have been developed, in the presence or absence of CrCl3 and TMSCl cocatalysts. The reactions are effective for a variety of N-aryl α-amino acids and have excellent functional group tolerance. The Cr-free conditions generally provide higher yields and avoid the use of chromium reagents. Further, the Cr-free conditions were extended to a series of N,N-dialkyl α-amino acid substrates. Mechanistic studies suggest that the Cr-mediated reaction proceeds predominantly via in situ formation of an alkyl-Cr intermediate while the Cr-free reaction proceeds largely via radical addition to a Brønsted acid-activated ketone. Chain propagation processes provide quantum yields of 5 and 10, respectively.

Challenges and Strategies for Synthesizing Glutamyl Hydrazide Containing Peptides

Herein, we detail several specific challenges that hinder the effective synthesis of glutamyl hydrazide containing peptides, and we describe a synthetic strategy to work around these challenges. Glutamyl hydrazide is an unnatural amino acid residue that bears an acyl hydrazide functional group on its side chain. This family of compounds has the potential to provide potent and selective inhibitor molecules for several families of enzymes. During peptide synthesis, however, these side chains—even in protected form—can derail the synthesis by initiating undesired side reactions. Avoiding these side reactions is critical for enabling effective access to this family of compounds.