Heterocyclic Cathinones as Inhibitors of Kynurenine Aminotransferase II-Design, Synthesis, and Evaluation

Ambient Temperature Cleavages of Amides in an Aqueous Medium for the Ipsilateral Effect of 1,8-Substituents on Naphthalene

The selective release of a molecule in its native form from a constructed framework is very attractive in the chemical and biological fields. The amide bond is ubiquitous in biological and chemical systems. However, the cleavage of an unmodified typical amide is a great challenge because of its high level of stabilization. Here, couplings of 8-azido-1-naphthoic acid prepared by us with amines afforded 8-azido-1-naphthamides. Reductions of 8-azido in 8-azido-1-naphthamides with sodium sulfide yielded 8-amino-1-naphthamides, and then, fast intramolecular nucleophilic attack of 8-amino to carbonyl of 1-amido in the presence of silica gel as the additive afforded 2,3-benzo[cd]indol-2(1H)-one freeing amines in almost quantitative conversion rates for the ipsilateral effect of 1,8-substituents on naphthalene. Furthermore, this strategy was extended to the cleavages of esters (alkyl 8-azido-1-naphthoates) successfully. The cleavages of amides and esters were performed in an aqueous medium at room temperature with wide functional group tolerance and were suitable for gram-scale production.

Identification of Two Flavonoids as New and Safe Inhibitors of Kynurenine Aminotransferase II via Computational and In Vitro Study

Background/Objectives: Kynurenine aminotransferase II (KAT-II) is a target for treating several diseases characterized by an excess of kynurenic acid (KYNA). Although KAT-II inactivators are available, they often lead to adverse side effects due to their irreversible inhibition mechanism. This study aimed to identify potent and safe inhibitors of KAT-II using computational and in vitro approaches. Methods: Virtual screening, MM/GBSA, and molecular dynamics simulations were conducted to identify the top drug candidates, followed by kinetic measurements and in vitro cytotoxicity evaluation. Results: The study showed that two compounds, herbacetin and (-)-Epicatechin exhibited the best scores. Their Glide docking scores are -8.66 kcal/mol and -8.16 kcal/mol, respectively, and their MM/GBSA binding energies are -50.30 kcal/mol and -51.35 kcal/mol, respectively. These scores are superior to those of the standard inhibitor, PF-04859989, which has docking scores of -7.12 kcal/mol and binding energy of -38.41 kcal/mol. ADMET analysis revealed that the selected compounds have favorable pharmacokinetic parameters, moderate bioavailability, and a safe toxicity profile, which supports their potential use. Further, the kinetic study showed that herbacetin and (-)-Epicatechin are reversible KAT-II inhibitors and exhibit a competitive inhibition mechanism. Their half-maximal inhibitory concentrations (IC50) are 5.98 ± 0.18 µM and 8.76 ± 0.76 µM, respectively. The MTT assay for cell toxicity indicated that the two compounds do not affect HepG2 cell viability at the necessary concentration for KAT-II inhibition. Conclusions: These results suggest that herbacetin and (-)-Epicatechin are suitable for KAT-II inhibition and are promising candidates for further development of KAT-II inhibitors.

Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

Modulation of T cells by tryptophan metabolites in the kynurenine pathway

Lymphocytes maturing in the thymus (T cells) are key factors in adaptive immunity and the regulation of inflammation. The kynurenine pathway of tryptophan metabolism includes several enzymes and compounds that can modulate T cell function, but manipulating these pharmacologically has not achieved the expected therapeutic activity for the treatment of autoimmune disorders and cancer. With increasing knowledge of other pathways interacting with kynurenines, the expansion of screening methods, and the application of virtual techniques to understanding enzyme structures and mechanisms, details of interactions between kynurenines and other pathways are being revealed. This review surveys some of these alternative approaches to influence T cell function indirectly via the kynurenine pathway and summarizes the most recent work on the development of compounds acting directly on the kynurenine pathway.