JAML promotes acute kidney injury mainly through a macrophage-dependent mechanism.

Although macrophages are undoubtedly attractive therapeutic targets for acute kidney injury (AKI) because of their critical roles in renal inflammation and repair, the underlying mechanisms of macrophage phenotype switching and efferocytosis in the regulation of inflammatory responses during AKI are still largely unclear. The present study elucidated the role of junctional adhesion molecule-like protein (JAML) in the pathogenesis of AKI. We found that JAML was significantly upregulated in kidneys from 2 different murine AKI models including renal ischemia/reperfusion injury (IRI) and cisplatin-induced AKI. By generation of bone marrow chimeric mice, macrophage-specific and tubular cell-specific Jaml conditional knockout mice, we demonstrated JAML promoted AKI mainly via a macrophage-dependent mechanism and found that JAML-mediated macrophage phenotype polarization and efferocytosis is one of the critical signal transduction pathways linking inflammatory responses to AKI. Mechanistically, the effects of JAML on the regulation of macrophages were, at least in part, associated with a macrophage-inducible C-type lectin-dependent mechanism. Collectively, our studies explore for the first time to our knowledge new biological functions of JAML in macrophages and conclude that JAML is an important mediator and biomarker of AKI. Pharmacological targeting of JAML-mediated signaling pathways at multiple levels may provide a novel therapeutic strategy for patients with AKI.

FGFR2-BRD4 Axis Regulates Transcriptional Networks of Histone 3 Modification and Synergy Between Its Inhibitors and PD-1/PD-L1 in a TNBC Mouse Model.

Epigenetic reprogramming is an independent mode of gene expression that often involves changes in the transcription and chromatin structure due to tumor initiation and development. In this study, we developed a specifically modified peptide array and searched for a recognized epigenetic reader. Our results demonstrated that BRD4 is not only an acetylation reader but of propionylation as well. We also studied the quantitative binding affinities between modified peptides and epigenetic regulators by isothermal titration calorimetry (ITC). Furthermore, we introduced the Fgfr2-S252W transgenic mouse model to confirm that this acetylation is associated with the activation of c-Myc and drives tumor formation. Targeted disruption of BRD4 in Fgfr2-S252W mouse tumor cells also confirmed that BRD4 is a key regulator of histone 3 acetylation. Finally, we developed a tumor slice culture system and demonstrated the synergy between immune checkpoint blockade and targeted therapy in triple-negative breast cancer (TNBC). These data extend our understanding of epigenetic reprogramming and epigenetics-based therapies.

Chemical Biology Tools for Protein Lysine Acylation.

Lysine acylation plays pivotal roles in cell physiology, including DNA transcription and repair, signal transduction, immune defense, metabolism, and many other key cellular processes. Molecular mechanisms of dysregulated lysine acylation are closely involved in the pathophysiological progress of many human diseases, most notably cancers. In recent years, chemical biology tools have become instrumental in studying the function of post-translational modifications (PTMs), identifying new "writers", "erasers" and "readers", and in targeted therapies. Here, we describe key developments in chemical biology approaches that have advanced the study of lysine acylation and its regulatory proteins (2016-2021). We further discuss the discovery of ligands (inhibitors and PROTACs) that are capable of targeting regulators of lysine acylation. Next, we discuss some current challenges of these chemical biology probes and suggest how chemists and biologists can utilize chemical probes with more discriminating capacity. Finally, we suggest some critical considerations in future studies of PTMs from our perspective.

Natural STAT3 inhibitors: A mini perspective.

Signal transducer and activator of transcription 3 (STAT3) plays pivotal role in several cellular processes such as cell proliferation and survival and has been found to be aberrantly activated in many cancers. STAT3 is largely believed to be one of the key oncogenes and crucial therapeutic targets. Much research has suggested the leading mechanisms for regulating the STAT3 pathway and its role in promoting tumorigenesis. Therefore, intensive efforts have been devoted to develop potent STAT3 inhibitors and several of them are currently undergoing clinical trials. Nevertheless, many natural products were identified as STAT3 inhibitors but attract less attention compared to the small molecule counterpart. In this review, the development of natural STAT3 inhibitors with an emphasis on their biological profile and chemical synthesis are detailed. The current state of STAT3 inhibitors and the future directions and opportunities for STAT3 inhibitor are discussed.

Chemical Probes Reveal Sirt2's New Function as a Robust "Eraser" of Lysine Lipoylation.

Lysine lipoylation, a highly conserved lysine post-translational modification, plays a critical role in regulating cell metabolism. The catalytic activity of a number of vital metabolic proteins, such as pyruvate dehydrogenase (PDH), depends on lysine lipoylation. Despite its important roles, the detailed biological regulatory mechanism of lysine lipoylation remains largely unexplored. Herein we designed a powerful affinity-based probe, KPlip, to interrogate the interactions of lipoylated peptide/proteins under native cellular environment. Large-scale chemical proteomics analysis revealed a number of binding proteins of KPlip, including sirtuin 2 (Sirt2), an NAD+-dependent protein deacylase. To explore the potential activity of Sirt2 toward lysine lipoylation, we designed a single-step fluorogenic probe, KTlip, which reports delipoylation activity in a continuous manner. The results showed that Sirt2 led to significant delipoylation of KTlip, displaying up to a 60-fold fluorescence increase in the assay. Further kinetic experiments with different peptide substrates revealed that Sirt2 can catalyze the delipoylation of peptide (DLAT-PDH, K259) with a remarkable catalytic efficiency (kcat/Km) of 3.26 × 103 s-1 M-1. The activity is about 400-fold higher than that of Sirt4, the only mammalian enzyme with known delipoylation activity. Furthermore, overexpression and silencing experiments demonstrated that Sirt2 regulates the lipoylation level and the activity of endogenous PDH, thus unequivocally confirming that PDH is a genuine physiological substrate of Sirt2. Using our chemical probes, we have successfully established the relationship between Sirt2 and lysine lipoylation in living cells for the first time. We envision that such chemical probes will serve as useful tools for delineating the roles of lysine lipoylation in biology and diseases.

Water-Soluble Polythiophene for Two-Photon Excitation Fluorescence Imaging and Photodynamic Therapy of Cancer.

Positively charged water-soluble polythiophene (PT0) that could self-assemble into nanoparticles in pure water solution was designed and synthesized. PT0 exhibited high photostabilities and pH stabilities, excellent biocompatibility, strong 1O2 generation capability, and large two-photon absorption cross sections. Moreover, we showed that the fluorescence of PT0 was unaffected by the interference of biomolecules and metal ions. As an example application, PT0 was demonstrated to be capable of simultaneous cell imaging and photodynamic therapy under either one-photon or two-photon excitation modes.

Peptide-Decorated Gold Nanoparticles as Functional Nano-Capping Agent of Mesoporous Silica Container for Targeting Drug Delivery.

A stimuli-responsive drug delivery system (DDS) with bioactive surface is constructed by end-capping mesoporous silica nanoparticles (MSNs) with functional peptide-coated gold nanoparticles (GNPs). MSNs are first functionalized with acid-labile α-amide-ß-carboxyl groups to carry negative charges, and then capped with positively charged GNPs that are decorated with oligo-lysine-containing peptide. The resulting hybrid delivery system exhibits endo/lysosomal pH triggered drug release, and the incorporation of RGD peptide facilitates targeting delivery to αvß3 integrin overexpressing cancer cells. The system can serve as a platform for preparing diversified multifunctional nanocomposites using various functional inorganic nanoparticles and bioactive peptides.

Fluorescent probes for detecting monoamine oxidase activity and cell imaging.

A series of new fluorogenic probes for monoamine oxidases (MAOs) were reported based on an oxidation and ß-elimination mechanism. The limits of detection of the probes for MAO-A and -B were determined to be 3.5 and 6.0 µg mL(-1) respectively. These probes displayed strong activity towards MAOs, especially MAO-B. Cellular imaging studies were also successfully conducted with MCF-7 cells.

Nickel-catalyzed C-H direct amination of benzoxazoles with secondary amines.

In this article, a facile, efficient and practical method for Ni-catalyzed direct C-H amination of benzoxazole with secondary amines has been developed. This procedure requires Ni(OAc)(2)·4H(2)O as catalyst, TBHP as oxidant and acid as the additive. A variety of substituted benzoxazol-2-amines were synthesized in moderate to good yields.

Experimental study of podophyllotoxin dipalmitoylphosphatidylcholine liposome for topical skin application.

OBJECTIVE: To observe the drug release of podophyllotoxin liposome and the drug retention in the skin. METHODS: Two liposome suspensions containing respectively podophyllotoxin dipalmitoylphosphatidylcholine (DPPC) and soya bean lecithin were prepared ultrasonically. Podophyllotoxin anhydride and the liposome suspensions were applied onto the skin of young pigs to observe the drug retention in the skin at different time points in the following 2 days, with exclusive liposome or anhydride serving as control. RESULTS: One hour after application of podophyllotoxin anhydride, a peak of the drug concentration in the skin occurred followed by immediate declination, a process not observed after the application of bean lecithin liposome due to gradual drug release that produced drug concentration constantly much higher than that of podophyllotoxin anhydride. A peak concentration was also observed 4 h after application of podophyllotoxin DPPC liposome, which then declined slowly to and stabilized at a higher level than that of bean lecithin liposome of anhydride within 48 h. CONCLUSION: DPPC liposome-embedded podophyllotoxin better targets the drug to the skin after application, and is a suitable preparation for topical skin application.