Phosphatase, Mg2+/Mn2+ dependent 1B regulates the hematopoietic stem cells homeostasis via the Wnt/ß-catenin signaling.

Hematopoietic stem cells (HSC) are primarily dormant in a cell-cycle quiescence state to preserve their self-renewal capacity and long-term maintenance. How HSC maintain the balance between activation and quiescence remains largely unknown. Herein, we found that phosphatase, Mg2+/Mn2+ dependent 1B (Ppm1b) is required for the expansion of phenotypic HSC in vitro. By using a conditional knockout mouse model in which Ppm1b was specifically depleted in hematopoietic cells, we demonstrated that loss of Ppm1b impaired the HSC homeostasis and hematopoietic reconstitution. Ppm1b deficiency mice also exhibited B-cell leukocytopenia, which is due to the compromised commitment and proliferation of B-biased lymphoid progenitor cells from common lymphoid progenitors. With the aid of a small molecular inhibitor, we confirmed the roles of Ppm1b in adult hematopoiesis that phenocopied the effects with loss of Ppm1b. Furthermore, transcriptome profiling of Ppm1b-deficient HSC revealed the disruptive quiescence of HSC. Mechanistically, Ppm1b interacted with ß-catenin and mediated its dephosphorylation. Loss of Ppm1b led to the decrease in the active ß-catenin (non-phosphorylated) that interrupted the Wnt/ß-catenin signaling in HSC, which consequently suppressed HSC expansion. Together, our study identified an indispensable role for Ppm1b in regulating HSC homeostasis via the Wnt/ß-catenin pathway.

Transition Metal-Catalyzed Selective Carbon-Carbon Bond Cleavage of Vinylcyclopropanes in Cycloaddition Reactions.

In this review, transition metal-catalyzed methodologies and applications that exploit C-C bond cleavage of vinylcyclopropanes (VCPs) are summarized with a focus on cycloaddition and related addition reactions. Transition metals, including palladium, nickel, iron, ruthenium, rhodium, cobalt, and iridium, can catalyze the cleavage of C-C bonds in activated or nonactivated VCPs. Additionally, these bond-breaking reactions can occur as intra- or intermolecular processes. The properties of activated and nonactivated VCPs are discussed in the Introduction. Various transition metal-catalyzed cycloaddition and addition reactions involving the cleavage of C-C bonds in activated VCPs are then discussed in the next chapter. The transition metal-catalyzed cycloadditions involving the cleavage of C-C in nonactivated VCPs are summarized in the following chapter. Finally, challenges and potential opportunities are outlined in the last chapter.

Synthesis of Lactams via Ir-Catalyzed C-H Amidation Involving Ir-Nitrene Intermediates.

x-membered lactams were synthesized via either an amidation of sp3 C-H bonds or an electrophilic substitution of arenes via Ir-nitrene intermediates. With the employment of a readily available iridium catalyst in dichloromethane or hexafluoro-2-propanol, a wide range of lactams were synthesized in good to excellent yields with high selectivity.

Discovery of 2,3'-diindolylmethanes as a novel class of PCSK9 modulators.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of low density lipoprotein receptor (LDLR). Anti-PCSK9 agents have been approved for the treatment of hypercholesterolemia. We recently discovered a series of small-molecule PCSK9 modulators that contains a relatively small pharmacophore of 2,3'-diindolylmethane with molecular weights around only 250. These molecules can significantly lower the amount of PCSK9 protein in a cell-based phenotypic assay. Our SAR studies yielded compound 16 with a IC50-value of 200 nM. No obvious cytotoxicity was observed at concentrations below 50 µM.

Rhodium-Catalyzed Intramolecular [5+2] Cycloaddition of Inverted 3-Acyloxy-1,4-enyne and Alkyne: Experimental and Theoretical Studies.

By switching the position of the alkene and alkyne, a new type of 3-acyloxy-1,4-enyne (ACE) five-carbon building block was developed for Rh-catalyzed intramolecular [5+2] cycloaddition. An electron-withdrawing acyl group on the alkyne termini of the ACE was essential for a regioselective 1,2-acyloxy migration. This new method provided bicyclic [5.3.0]decatrienes that are different from previous methods because of the positions of the alkenes and the acyloxy group. Multiple mechanistic pathways become possible for this new [5+2] cycloaddition and they are investigated by computational studies.

Rhodium(I)-Catalyzed Benzannulation of Heteroaryl Propargylic Esters: Synthesis of Indoles and Related Heterocycles.

A de novo synthesis of a benzene ring allows for the preparation of a diverse range of heterocycles including indoles, benzofurans, benzothiophenes, carbazoles, and dibenzofurans from simple heteroaryl propargylic esters using a unified carbonylative benzannulation strategy. Multiple substituents can be easily introduced to the C4-C7 positions of indoles and related heterocycles.

Synthesis of Carbazoles and Carbazole-Containing Heterocycles via Rhodium-Catalyzed Tandem Carbonylative Benzannulations.

Polycyclic aromatic compounds are important constituents of pharmaceuticals and other materials. We have developed a series of Rh-catalyzed tandem carbonylative benzannulations for the synthesis of tri-, tetra-, and pentacyclic heterocycles from different types of aryl propargylic alcohols. These tandem reactions provide efficient access to highly substituted carbazoles, furocarbazoles, pyrrolocarbazoles, thiophenocarbazoles, and indolocarbazoles. While tricyclic heterocycles could be derived from vinyl aryl propargylic alcohols, tetra- and pentacyclic heterocycles were synthesized from diaryl propargylic alcohols. The tandem carbonylative benzannulation is initiated by a π-acidic rhodium(I) catalyst-mediated nucleophilic addition to alkyne to generate a key metal-carbene intermediate, which is then trapped by carbon monoxide to form a ketene species for 6π electrocyclization. Overall, three bonds and two rings are formed in all of these tandem carbonylative benzannulation reactions.

Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations.

Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition-metal catalysts were employed.

Overcoming the blood-brain barrier in chemotherapy treatment of pediatric brain tumors.

Pediatric brain tumors are most common cancers in childhood and among the leading causes of death in children. Chemotherapy has been used as adjuvant (i.e. after) or neoadjuvant (i.e. before) therapy to surgery and radiotherapy for the management of pediatric brain tumors for more than four decades and gained more attention in the recent two decades. Although chemotherapy has demonstrated its effectiveness in the management of some pediatric brain tumors, failure or inactiveness of chemotherapy is commonly met in the clinics and clinical trials. Some of these failures might be attributed to the blood-brain barrier (BBB), limiting the penetration of systemically administered chemotherapeutics into pediatric brain tumors. Therefore, various strategies have been developed and used to address this issue. Herein, we review different methods reported in the literature to circumvent the BBB for enhancing the present of chemotherapeutics in the brain to treat pediatric brain tumors.

3-Acyloxy-1,4-enyne: a New Five-carbon Synthon for Rhodium-Catalyzed (5+2) Cycloadditions.

Seven-membered rings are ubiquitous in natural products and pharmaceutical agents and their syntheses continue to stimulate the development of novel synthetic methods. The (5+2) cycloaddition is one of the most efficient ways to access seven-membered rings since the 2-carbon components (alkenes, alkynes, or allenes) are readily available. Prior to our study, however, there was only one type of transition metal-catalyzed (5+2) cycloaddition: the reaction between vinylcyclopropanes and alkenes, alkynes, or allenes. We recently developed a new type of transition metal-catalyzed (5+2) cycloaddition, where the 5-carbon building block is 3-acyloxy-1,4-enyne (ACE). Our recent progress on Rh-catalyzed intra- and intermolecular (5+2) cycloadditions of ACEs and alkynes is summarized in this article. Using chiral propargylic esters, bicyclic products were prepared in high optical purity by the intramolecular (5+2) cycloadditions. Monocyclic seven-membered rings were synthesized by intermolecular (5+2) cycloaddition of ACEs and alkynes. Kinetic studies indicated that the rate of this intermolecular cycloaddition was significantly accelerated when the acetate was replaced by dimethylaminobenzoate. DFT calculations suggested that novel metallacycles were generated by a Rh-promoted oxidative cycloaddition of 1,4-enynes accompanied by a 1,2-acyloxy migration of propargylic esters.

Kinetic resolution of 1-(1-alkynyl)cyclopropyl ketones via gold-catalyzed divergent (4 + 4) cycloadditions: stereoselective access to furan fused eight-membered heterocycles.

Chiral eight-membered heterocycles comprise a diverse array of natural products and bioactive compounds, yet accessing them poses significant challenges. Here we report a gold-catalyzed stereoselective (4 + 4) cycloaddition as a reliable and divergent strategy, enabling readily accessible precursors (anthranils and ortho-quinone methides) to be intercepted by in situ generated gold-furyl 1,4-dipoles, delivering previously inaccessible chiral furan/pyrrole-containing eight-membered heterocycles with good results (56 examples, all >20 : 1 dr, up to 99% ee). Moreover, we achieve a remarkably efficient kinetic resolution (KR) process (s factor up to 747). The scale-up synthesis and diversified transformations of cycloadducts highlight the synthetic potential of this protocol. Computational calculations provide an in-depth understanding of the stereoselective cycloaddition process.

Comparison of the components of fresh Panax notoginseng processed by different methods and their anti-anemia effects on cyclophosphamide-treated mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The traditional Chinese herb Panax notoginseng (PN) tonifies blood, and its main active ingredient is saponin. PN is processed by different methods, resulting in different compositions and effects. AIM OF THE STUDY: To investigate changes in the microstructure and composition of fresh PN processed by different techniques and the anti-anemia effects on tumor-bearing BALB/c mice after chemotherapy with cyclophosphamide (CTX). MATERIALS AND METHODS: Fresh PN was processed by hot-air drying (raw PN, RPN), steamed at 120 °C for 5 h (steamed PN, SPN), or fried at 130 °C, 160 °C, or 200 °C for 8 min (fried PN, FPN1, FPN2, or FPN3, respectively); then, the microstructures were compared with 3D optical microscopy, quasi-targeted metabolites were detected by liquid chromatography tandem mass spectrometry (LC‒MS/MS), and saponins were detected by high-performance liquid chromatography (HPLC). An anemic mouse model was established by subcutaneous H22 cell injection and treatment with CTX. The antianemia effects of PN after processing via three methods were investigated by measuring peripheral blood parameters, performing HE staining and measuring cell proliferation via immunofluorescence. RESULTS: 3D optical profiling revealed that the surface roughness of the SPN and FPN was greater than that of the other materials. Quasi-targeted metabolomics revealed that SPN and FPN had more differentially abundant metabolites whose abundance increased, while SPN had greater amounts of terpenoids and flavones. Analysis of the composition and content of the targeted saponins revealed that the contents of rare saponins (ginsenoside Rh1, 20(S)-Rg3, 20(R)-Rg3, Rh4, Rk3, Rg5) were greater in the SPN. In animal experiments, the RBC, WBC, HGB and HCT levels in peripheral blood were increased by SPN and FPN. HE staining and immunofluorescence showed that H-SPN and M-FPN promoted bone marrow and spleen cell proliferation. CONCLUSION: The microstructure and components of fresh PN differed after processing via different methods. SPN and FPN ameliorated CTX-induced anemia in mice, but the effects of PN processed by these two methods did not differ.

Injectable thermosensitive selenium-containing hydrogel as mesenchymal stem cell carrier to improve treatment efficiency in limb ischemia.

Limb ischemia is a refractory disease characterized by persistent inflammation, insufficient angiogenesis, and tissue necrosis. Although mesenchymal stem cells (MSCs) have shown potential for treating limb ischemia, their therapeutic effects are limited by low engraftment rates. Therefore, developing an optimal MSC delivery system that enhances cell viability is imperative. Selenium, known for its cytoprotective properties in various cell types, offers a potential strategy to enhance therapeutic effect of MSCs. In this study, we evaluated the cytoprotective effects of selenium on MSCs, and developed an injectable thermosensitive selenium-containing hydrogel based on PLGA-PEG-PLGA triblock copolymer, as a cell carrier to improve MSC viability after engraftment. The biocompatibility, biodegradability, and cytoprotective capabilities of selenium-containing hydrogels were assessed. Furthermore, the therapeutic potential of MSCs encapsulated within a thermosensitive selenium-containing hydrogel in limb ischemia was evaluated using cellular and animal experiments. Selenium protects MSCs from oxidative damage by upregulating GPX4 through a transcriptional mechanism. The injectable thermosensitive selenium-containing hydrogel exhibited favorable biocompatibility, biodegradability, and antioxidant properties. It can be easily injected into the target area in liquid form at room temperature and undergoes gelation at body temperature, thereby preventing the diffusion of selenium and promoting the cytoprotection of MSCs. Furthermore, MSCs encapsulated within the selenium-containing hydrogel effectively inhibited macrophage M1 polarization while promoting macrophage M2 polarization, thus accelerating angiogenesis and restoring blood perfusion in ischemic limbs. This study demonstrated the potential of an injectable thermosensitive selenium-containing hydrogel as a promising method for MSC delivery. By addressing the challenge of low retention rate, which is a major obstacle in MSC application, this strategy effectively improves limb ischemia.

Tethered spectroscopic probes estimate dynamic distances with subnanometer resolution in voltage-dependent potassium channels.

Measurements of inter- and intramolecular distances are important for monitoring structural changes and understanding protein interaction networks. Fluorescence resonance energy transfer and functionalized chemical spacers are the two predominantly used strategies to map short-range distances in living cells. Here, we describe the development of a hybrid approach that combines the key advantages of spectroscopic and chemical methods to estimate dynamic distance information from labeled proteins. Bifunctional spectroscopic probes were designed to make use of adaptable-anchor and length-varied spacers to estimate molecular distances by exploiting short-range collisional electron transfer. The spacers were calibrated using labeled polyproline peptides of defined lengths and validated by molecular simulations. This approach was extended to estimate distance restraints that enable us to evaluate the resting-state model of the Shaker potassium channel.

Rhodium-catalyzed tandem annulation and (5 + 1) cycloaddition: 3-hydroxy-1,4-enyne as the 5-carbon component.

A Rh-catalyzed tandem annulation and (5 + 1) cycloaddition was realized. 3-Hydroxy-1,4-enyne served as the new 5-carbon component for the (5 + 1) cycloaddition. Substituted carbazoles, dibenzofurans, and tricyclic compounds containing a cyclohexadienone moiety could be prepared efficiently. The identification of a byproduct suggests that metal carbene and ketene intermediates may be involved in the (5 + 1) cycloaddition.

Rhodium-catalyzed intra- and intermolecular [5 + 2] cycloaddition of 3-acyloxy-1,4-enyne and alkyne with concomitant 1,2-acyloxy migration.

A new type of rhodium-catalyzed [5 + 2] cycloaddition was developed for the synthesis of seven-membered rings with diverse functionalities. The ring formation was accompanied by a 1,2-acyloxy migration event. The five- and two-carbon components of the cycloaddition are 3-acyloxy-1,4-enynes (ACEs) and alkynes, respectively. Cationic rhodium(I) catalysts worked most efficiently for the intramolecular cycloaddition, while only neutral rhodium(I) complexes could facilitate the intermolecular reaction. In both cases, electron-poor phosphite or phosphine ligands often improved the efficiency of the cycloadditions. The scope of ACEs and alkynes was investigated in both the intra- and intermolecular reactions. The resulting seven-membered-ring products have three double bonds that could be selectively functionalized.

Rhodium-catalyzed carbonylation of cyclopropyl substituted propargyl esters: a tandem 1,3-acyloxy migration [5 + 1] cycloaddition.

We have developed two different types of tandem reactions for the synthesis of highly functionalized cyclohexenones from cyclopropyl substituted propargyl esters. Both reactions were initiated by rhodium-catalyzed Saucy-Marbet 1,3-acyloxy migration. The resulting cyclopropyl substituted allenes derived from acyloxy migration then underwent [5 + 1] cycloaddition with CO. The acyloxy group not only eased the access to allene intermediates but also provided a handle for further selective functionalizations.

Asymmetric ß-arylation of cyclopropanols enabled by photoredox and nickel dual catalysis.

The enantioselective functionalization and transformation of readily available cyclopropyl compounds are synthetically appealing yet challenging topics in organic synthesis. Here we report an asymmetric ß-arylation of cyclopropanols with aryl bromides enabled by photoredox and nickel dual catalysis. This dual catalytic transformation features a broad substrate scope and good functional group tolerance at room temperature, providing facile access to a wide array of enantioenriched ß-aryl ketones bearing a primary alcohol moiety in good yields with satisfactory enantioselectivities (39 examples, up to 83% yield and 90% ee). The synthetic value of this protocol was illustrated by the concise asymmetric construction of natural product calyxolane B analogues.

Inhaled mRNA Nanoformulation with Biogenic Ribosomal Protein Reverses Established Pulmonary Fibrosis in a Bleomycin-Induced Murine Model.

Idiopathic pulmonary fibrosis (IPF), a lethal respiratory disease with few treatment options, occurs due to repetitive microinjuries to alveolar epithelial cells (AECs) and progresses with an overwhelming deposition of extracellular matrix (ECM), ultimately resulting in fibrotic scars and destroyed the alveolar architecture. Here, an inhaled ribosomal protein-based mRNA nanoformulation is reported for clearing the intrapulmonary ECM and re-epithelializing the disrupted alveolar epithelium, thereby reversing established fibrotic foci in IPF. The nanoformulation is sequentially assembled by a ribosomal protein-condensed mRNA core, a bifunctional peptide-modified corona and keratinocyte growth factor (KGF) with a PEGylated shielding shell. When inhaled via a nebulizer, the nanoformulations carried by microdrops are deposited in the alveoli, and penetrate into fibrotic foci, where the outer KGFs are detached after matrix metalloproteinase 2 (MMP2) triggering. The RGD motif-grafted cores then expose and specifically target the integrin-elevated cells for the intracellular delivery of mRNA. Notably, repeated inhalation of the nanoformulations accelerates the clearance of locoregional collagen by boosting the intralesional expression of MMP13 and alveolar re-epithelialization mediated by KGFs, which synergistically ameliorates the lung function of a bleomycin-induced murine model. Therefore, this work provides an alternative mRNA-inhalation delivery strategy, which shows great potential for the treatment of IPF.