Chuan Bai

The plasmid-encoded phosphoethanolamine transferase (MCR-1) impairs the efficacy of colistin, a last-line antibiotic for multidrug-resistant Gram-negative bacteria. To address this antibiotic resistance challenge, we designed and synthesized a series of benzopyran derivatives as MCR-1 inhibitors. Among these, compound 65 potently restored colistin susceptibility in clinical mobilized colistin resistance-1 (mcr-1)-positive Escherichia coli (E. coli) strains, showing a 14-fold enhancement compared to the initial hit. Mechanism of action studies confirmed that compound 65 bound directly to MCR-1 and inhibited its enzymatic activity. Molecular docking and mutagenesis assays suggested that compound 65 engages multiple residues within the catalytic pocket of the MCR-1 protein. In a murine peritonitis infection model, the combination of compound 65 and colistin significantly improved the survival rates and reduced bacterial loads. These results highlight the promising potential of benzopyran derivatives, especially compound 65, as adjuvants for counteracting colistin resistance mediated by MCR-1.

Electrophilic compounds from natural products (NPs) and metabolites can covalently modify the cysteines of target proteins to induce biological activities. To facilitate the discovery of novel NPs and metabolites, chemical probes with various thiol groups—mimicking the reactivity of cysteine—have been developed. These probes are designed to react with electrophilic groups of NPs and metabolites in an electrophilic addition mechanism, with the resulting adducts having molecular masses which equal to the sum of the probe and the target compound. This principle has been fundamental to analyzing mass spectrometry (MS) data and calculating the exact molecular weights of the target compound. In this study, we report a phenol thiol probe initially designed to mimic cysteine reacts with Mollugin and other structurally related NPs in an electrophilic free radical addition mechanism, and thus leads to the incorporation of not only the thiol probe but also a hydroxyl group in the adducts. Our results demonstrate that the phenol thiol group of the probe cannot always represent the thiol in cysteine to discover novel NPs or metabolites that can covalently modify cysteines.

Lipid peroxidation, the key step in the ferroptosis process, requires the oxidation of the double bonds of phospholipids in cellular membrane structures. Current research on ferroptosis mechanisms and new drug development has focused on naturally occurring phospholipids with internal double bonds. However, whether unnatural terminal double bonds can be involved in ferroptosis remains to be elucidated. In this study, we introduced terminal double bonds at the sn-2 position of phospholipids (Terminal Olefin Fatty Acids, TOFA) and discovered that these artificial phospholipids can kill cells alone, without ferroptosis inducers, and can be inhibited only by some ferroptosis inhibitors, such as ferrostatin-1, liproxstatin-1, alpha-tocopherol, but not deferoxamine mesylate. Our results reveal that phospholipids with terminal double bonds can participate in ferroptosis through an atypical mechanism. Moreover, further mechanistic studies could confirm that controlling the double bond position could be useful to maneuver ferroptosis and develop new drugs.

A right aortic arch with concomitant right patent ductus arteriosus and right tracheal bronchus is a rare congenital anomaly. Herein, the respiratory and circulatory functions of the child were normal at early ages, and imaging examination indicated that conservative treatment was suitable. However, with the growth and development of the child, the right tracheal bronchus was oppressed by the right arterial duct. We performed a cut and ligation of the right patent ductus arteriosus to relieve the pressure on the right tracheal bronchus. At the 6-month follow-up, the child had recovered well and exhibited no symptoms of respiratory restriction. Therefore, we believe that early interventions should be considered for this rare anatomic presentation to benefit the patient’s respiratory and circulatory systems. Our experience provides a foundational reference for future cases.

The vital roles of biologically relevant cysteines have been discovered from proteins that are promising targets for new drugs or chemical tools. Therefore, new electrophilic small molecules that can covalently modulate these cysteines have attracted immense interest. Because of their extremely wide chemical diversity, electrophilic natural products (NPs) have been studied as promising sources of cysteine modulators. Previous studies have developed chemical probes to facilitate the detection and isolation of electrophilic NPs. To address the problems with the current methods, including their low sensitivity, high false-positive rate, and dependence on performing manual processing with a plethora of spectra, we report a chemical probe that can first covalently capture electrophilic NPs from natural resources and then produce sensitive reporter ion signals that are specific for the detected NPs. We applied this untargeted method to explore electrophilic NPs from natural resources and found that the complexity of electrophilic NPs was beyond our expectations. We used this chemical probe to identify a new electrophilic furanosesterterpene (BG-1) from an extract of Ginkgo biloba that targets the Cys207 of acyl-CoA thioesterase 7 (ACOT7).

Retinoic‑acid‑receptor‑related orphan nuclear hormone receptor gamma t (RORγt), a critical transcriptional factor of Th17 cells, is a potential therapeutic target for Th17-mediated autoimmune diseases. In addition, RORγt is essential for thymocyte survival and lymph node development, and RORγt inhibition or deficiency causes abnormal thymocyte development, thymus lymphoma, and lymph node defect. Recent study demonstrated that specific regulation of Th17 differentiation related to the hinge region of RORγt. In this research, we investigated the effect of RORγt inhibitor, 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivative (TTP), in the therapy of lupus nephritis and its safety on thymocyte development. We demonstrated that TTP repressed the development of Th17 cells and ameliorated the autoimmune disease manifestation in the pristane-induced lupus nephritis mice model. The treatment of TTP in the mice did not interfere with thymocyte development, including total thymocyte number and proportion of CD4⁺CD8⁺ double-positive populations in the thymus, and had no substantial effects on the pathogenesis of thymoma. The TTP had a stronger affinity with full-length RORγt protein compared with the truncated RORγt LBD region via surface plasmon resonance, which indicated TTP binding to RORγt beyond LBD region. Molecular docking computation showed that the best binding pocket of TTP to RORγt is located in the hinge region of RORγt. In summary, as a RORγt inhibitor, TTP had a potential to develop the clinical medicine for treating Th17-mediated autoimmune diseases with low safety risk for thymocyte development.

Scope: Crocins are important apocarotenoids in the extract of saffron (Crocus sativus L.) and fruits of gardenia (Gardenia jasminoides E.). Crocins have shown versatile biological activities and thus they have been considered to be promising therapeutics for neurodegenerative and heart diseases. Metabolism studies report that crocetin‐monoglucuronide (CM) is produced and detected in rat blood plasma after oral administration of crocins. However, due to the lack of standard compound of CM, its unambiguous identification, quantification, and bioactivity studies have been hindered.Methods and results: CM is synthetized and its existence in blood plasma in Sprague–Dawley (SD) rats is quantified. The pharmacokinetic studies show that CM is produced in blood and brain after oral administration of crocin‐1. It is then discovered that CM possesses neuroprotective activity against beta‐amyloid (Aβ) toxicity in PC‐12 cells and drosophila models. The enzymatic assay shows that CM can effectively inhibit AChE and docking studies indicate that CM may bind in the gorge channel of AChE.Conclusion: The work discovered that CM is a neuron‐protective metabolite of the orally administrated crocin‐1. It is demonstrated that AChE can be one of the targets of CM in its neuron‐protective activity.