Structural Basis of H2B Ubiquitination-Dependent H3K4 Methylation by COMPASS.

The COMPASS (complex of proteins associated with Set1) complex represents the prototype of the SET1/MLL family of methyltransferases that controls gene transcription by H3K4 methylation (H3K4me). Although H2B monoubiquitination (H2Bub) is well known as a prerequisite histone mark for COMPASS activity, how H2Bub activates COMPASS remains unclear. Here, we report the cryoelectron microscopy (cryo-EM) structures of an extended COMPASS catalytic module (CM) bound to the H2Bub and free nucleosome. The COMPASS CM clamps onto the nucleosome disk-face via an extensive interface to capture the flexible H3 N-terminal tail. The interface also sandwiches a critical Set1 arginine-rich motif (ARM) that autoinhibits COMPASS. Unexpectedly, without enhancing COMPASS-nucleosome interaction, H2Bub activates the enzymatic assembly by packing against Swd1 and alleviating the inhibitory effect of the Set1 ARM upon fastening it to the acidic patch. By delineating the spatial configuration of the COMPASS-H2Bub-nucleosome assembly, our studies establish the structural framework for understanding the long-studied H2Bub-H3K4me histone modification crosstalk.

O→S Relay Deprotection: A General Approach to Controllable Donors of Reactive Sulfur Species.

Reactive sulfur species (RSS) are biologically important molecules. Among them, H2 S, hydrogen polysulfides (H2 Sn, n>1), persulfides (RSSH), and HSNO are believed to play regulatory roles in sulfur-related redox biology. However, these molecules are unstable and difficult to handle. Having access to their reliable and controllable precursors (or donors) is the prerequisite for the study of these sulfur species. Reported in this work is the preparation and evaluation of a series of O-silyl-mercaptan-based sulfur-containing molecules which undergo pH- or F- -mediated desilylation to release the corresponding H2 S, H2 Sn , RSSH, and HSNO in a controlled fashion. This O→S relay deprotection serves as a general strategy for the design of pH- or F- -triggered RSS donors. Moreover, we have demonstrated that the O-silyl groups in the donors could be changed into other protecting groups like esters. This work should allow the development of RSS donors with other activation mechanisms (such as esterase-activated donors).

A novel pH-controlled hydrogen sulfide donor protects gastric mucosa from aspirin-induced injury.

Hydrogen sulphide (H2 S) serves as a vital gastric mucosal defence under acid condition. Non-steroidal anti-inflammatory drugs (NSAIDs) are among widely prescribed medications with effects of antipyresis, analgesia and anti-inflammation. However, their inappropriate use causes gastric lesions and endogenous H2 S deficiency. In this work, we reported the roles of a novel pH-controlled H2 S donor (JK-1) in NSAID-related gastric lesions. We found that JK-1 could release H2 S under mild acidic pH and increase solution pH value. Intragastrical administration of aspirin (ASP), one of NSAIDs, to mice elicited significant gastric lesions, evidenced by mucosal festering and bleeding. It also led to infiltration of inflammatory cells and resultant releases of IL-6 and TNF-α, as well as oxidative injury including myeloperoxidase (MPO) induction and GSH depletion. In addition, the ASP administration statistically inhibited H2 S generation in gastric mucosa, while up-regulated cyclooxygenase (COX)-2 and cystathionine gamma lyase (CSE) expression. Importantly, these adverse effects of ASP were prevented by the intragastrical pre-administration of JK-1. However, JK-1 alone did not markedly alter the property of mouse stomachs. Furthermore, in vitro cellular experiments showed the exposure of gastric mucosal epithelial (GES-1) cells to HClO, imitating MPO-driven oxidative injury, decreased cell viability, increased apoptotic rate and damaged mitochondrial membrane potential, which were reversed by pre-treatment with JK-1. In conclusion, JK-1 was proved to be an acid-sensitive H2 S donor and could attenuate ASP-related gastric lesions through reconstruction of endogenous gastric defence. This work indicates the possible treatment of adverse effects of NSAIDs with pH-controlled H2 S donors in the future.

pH-Controlled Hydrogen Sulfide Release for Myocardial Ischemia-Reperfusion Injury.

Hydrogen sulfide (H2S) is a critical signaling molecule that regulates many physiological and/or pathological processes. Modulation of H2S levels could have potential therapeutic value. In this work, we report the rational design, synthesis, and biological evaluation of a class of phosphonamidothioate-based H2S-releasing agents (i.e., H2S donors). A novel pH-dependent intramolecular cyclization was employed to promote H2S release from the donors. These water-soluble compounds showed slow, controllable, and pH-sensitive production of H2S in aqueous solutions. The donors also showed significant cytoprotective effects in cellular models of oxidative damage. Most importantly, the donors were found to exhibit potent cardioprotective effects in an in vivo murine model of myocardial ischemia-reperfusion (MI/R) injury through a H2S-related mechanism.

Highly selective fluorescence off-on probes for biothiols and imaging in live cells.

Three sulfonyl benzothiazole-based fluorescent probes (, , and ) for the detection of biothiols (cysteine, homocysteine, and glutathione) are developed based on thiol-mediated nucleophilic aromatic substitutions. The probes exhibited good selectivity and sensitivity toward biothiols over other analytes. The probes were successfully applied for visualizing endogenous thiols in living cells.

A simple and sensitive differential digestion method to analyze adeno-associated virus residual host cell proteins by LC-MS.

Many methods using liquid chromatography-mass spectrometry (LC-MS) have been established for identifying residual host cell proteins (HCPs) to aid in the process development and quality control of therapeutic proteins. However, the use of MS-based techniques for adeno-associated virus (AAV) is still in its infancy, with few methods reported and minimal information available on potentially problematic HCPs. In this study, we developed a highly sensitive and effective differential digestion method to profile residual HCPs in AAV. Unlike direct digestion, which completely digests both AAV and HCPs, our differential digestion method takes advantage of AAV's unique characteristics to maintain the integrity of AAV while preferentially digesting HCPs under denaturing and reducing conditions. This differential digestion method requires only several micrograms of sample and significantly enhances the identification of HCPs. Furthermore, this method can be applied to all five different AAV serotypes for comprehensive HCP profiling. Our work fills a gap in AAV HCP analysis by providing a sensitive and robust strategy for detecting, monitoring, and measuring HCPs.

Driving technology factors of carbon emissions: Theoretical framework and its policy implications for China.

Empirical studies have widely examined the driving factors and methods to achieve a carbon peak; however, they seldom construct a theoretical framework and ignore the potential heterogeneity in technology. The most notable controversy is technology's different roles in carbon emissions. This study proposes an integrated theoretical framework considering the evolution of carbon emissions and presents the conditions for achieving a carbon peak. This framework shows that if the positive role of eco-friendly technology in decreasing carbon emissions is larger than the negative role of production-oriented technology in increasing carbon emissions; thus, carbon emissions do not increase (i.e. carbon peak). Additionally, this framework addresses the controversy concerning the effect of technology on carbon emissions. Our empirical results from a city-level panel dataset show that China is still moving towards achieving carbon emission reduction. Analysis of the driving mechanism reveals that production-oriented technology increases carbon emissions by increasing the production scale, consequently demanding more energy and emitting more carbon dioxide.

Corrigendum: Treatment of surgical brain injury by immune tolerance induced by peripheral intravenous injection of biotargeting nanoparticles loaded with brain antigens.

[This corrects the article DOI: 10.3389/fimmu.2019.00743.].

BRCA1/BARD1 site-specific ubiquitylation of nucleosomal H2A is directed by BARD1.

Mutations in the E3 ubiquitin ligase RING domains of BRCA1/BARD1 predispose carriers to breast and ovarian cancers. We present the structure of the BRCA1/BARD1 RING heterodimer with the E2 enzyme UbcH5c bound to its cellular target, the nucleosome, along with biochemical data that explain how the complex selectively ubiquitylates lysines 125, 127 and 129 in the flexible C-terminal tail of H2A in a fully human system. The structure reveals that a novel BARD1-histone interface couples to a repositioning of UbcH5c compared to the structurally similar PRC1 E3 ligase Ring1b/Bmi1 that ubiquitylates H2A Lys119 in nucleosomes. This interface is sensitive to both H3 Lys79 methylation status and mutations found in individuals with cancer. Furthermore, NMR reveals an unexpected mode of E3-mediated substrate regulation through modulation of dynamics in the C-terminal tail of H2A. Our findings provide insight into how E3 ligases preferentially target nearby lysine residues in nucleosomes by a steric occlusion and distancing mechanism.

Treatment of Surgical Brain Injury by Immune Tolerance Induced by Peripheral Intravenous Injection of Biotargeting Nanoparticles Loaded With Brain Antigens.

Once excessive, neurological disorders associated with inflammatory conditions will inevitably cause secondary inflammatory damage to brain tissue. Immunosuppressive therapy can reduce the inflammatory state, but resulting infections can expose the patient to greater risk. Using specific immune tolerance organs or tissues from the body, brain antigen immune tolerance treatment can create a minimal immune response to the brain antigens that does not excessively affect the body's immunity. However, commonly used immune tolerance treatment approaches, such as those involving the nasal, gastrointestinal mucosa, thymus or liver portal vein injections, affect the clinical conversion of the therapy due to uncertain drug absorption, or inconvenient routes of administration. If hepatic portal intravenous injections of brain antigens could be replaced by normal peripheral venous infusion, the convenience of immune tolerance treatment could certainly be greatly increased. We attempted to encapsulate brain antigens with minimally immunogenic nanomaterials, to control the sizes of nanoparticles within the range of liver Kupffer cell phagocytosis and to coat the antigens with a coating material that had an affinity for liver cells. We injected these liver drug-loaded nanomaterials via peripheral intravenous injection. With the use of microparticles with liver characteristics, the brain antigens were transported into the liver out of the detection of immune armies in the blood. This approach has been demonstrated in rat models of surgical brain injury. It has been proven that the immune tolerance of brain antigens can be accomplished by peripheral intravenous infusion to achieve the effect of treating brain trauma after operations, which simplifies the clinical operation and could elicit substantial improvements in the future.

Novel H2S-Releasing hydrogel for wound repair via in situ polarization of M2 macrophages.

Hydrogen sulfide (H2S), as a gaseous messenger, exhibits potential therapeutic effects in biological and clinical applications. Herein, an in situ forming biomimetic hyaluronic acid (HA) hydrogel was used as a matrix to dope a pH-controllable H2S donor, JK1, to form a novel HA-JK1 hybrid system. This HA-JK1 hydrogel was designed as an ideal delivery scaffold for JK1 with pH-dependent prolonged H2S releasing profile. In vitro study suggested that JK1 could induce the polarization of M2 phenotype indicating a higher pro-healing efficiency of macrophages. The in vivo studies on dermal wounds showed that the HA-JK1 hybrid hydrogel significantly accelerated the wound regeneration process through enhanced re-epithelialization, collagen deposition, angiogenesis and cell proliferation. Furthermore, the in vivo results also demonstrated a higher level of M2 polarization in HA-JK1 treated group with reduced inflammation and improved wound remodeling effects, which was consistent with the in vitro results. These observations could be considered as a key to the efficient wound treatment. Therefore, we suggest that HA-JK1 can be used as a novel wound dressing material toward cutaneous wound model in vivo. This system should significantly enhance wound regeneration through the release of H2S that induces the expression of M2 macrophage phenotype.

pH and enzyme dual-responsive release of hydrogen sulfide for disc degeneration therapy.

Intervertebral disc degeneration (IDD) usually causes lower back and neck pain with a high incidence, which significantly reduces the life quality of patients. However, there is no effective treatment available currently. Our previous study has found that hydrogen sulfide (H2S) shows potential therapeutic effect toward IDD. However, the burst release and fast vanishing of H2S in the lesion severely limit its further application. Therefore, in this study, we develop a pH and enzyme dual-responsive H2S releasing hydrogel system to treat IDD. This hydrogel named Col-JK1 is quite stable under neutral conditions but rapidly releases H2S by responding to acidic pH and high matrix metalloproteinases (MMPs) levels in the pathological IDD environment. In vivo study firstly uncovered that Col-JK1 can effectively impede disc degeneration in a puncture-induced IDD rat model. Further in vitro studies reveal that Col-JK1 protects the disc from degeneration by inhibiting the apoptosis of nucleus pulposus (NP) cells and attenuating the degradation of the disc extracellular matrix (ECM). And the protective effect of Col-JK1 is attributed to its anti-inflammatory effects through the regulation of the NF-κB signaling pathway. Thus, our study provides a novel therapeutic option for IDD therapy by controlling the release of H2S.

Cyclic Acyl Disulfides and Acyl Selenylsulfides as the Precursors for Persulfides (RSSH), Selenylsulfides (RSeSH), and Hydrogen Sulfide (H2S).

The reactions of three model compounds (1-3) for cyclic acyl disulfides and cyclic acyl selenylsulfides are studied. These compounds were found to be effective precursors for persulfides (RSSH) and selenylsulfides (RSeSH) upon reacting with nucleophilic species. They could also act as H2S donors when interacting with cellular thiols. The most interesting discovery was the generation of RSeSH from compound 3 under mild conditions. Selenylsulfides (RSeSH) are expected to be important regulating molecules involved in Sec-related redox signaling. The method of producing RSeSH should allow researchers to better understand the chemical biology of RSeSH.

Thiol-Activated Hydrogen Sulfide Donors Antiviral and Anti-Inflammatory Activity in Respiratory Syncytial Virus Infection.

We have recently shown that endogenous hydrogen sulfide (H2S), an important cellular gaseous mediator, exerts an antiviral and anti-inflammatory activity in vitro and in vivo, and that exogenous H2S delivered via the synthetic H2S-releasing compound GYY4137 also has similar properties. In this study, we sought to extend our findings to a novel class of H2S donors, thiol-activated gem-dithiol-based (TAGDDs). In an in vitro model of human respiratory syncytial virus (RSV) infection, TAGDD-1 treatment significantly reduced viral replication, even when added up to six hours after infection. Using a mouse model of RSV infection, intranasal delivery of TAGDD-1 to infected mice significantly reduced viral replication and lung inflammation, markedly improving clinical disease parameters and pulmonary dysfunction, compared to vehicle treated controls. Overall our results indicate that this novel synthetic class of H2S-releasing compounds exerts antiviral and anti-inflammatory activity in the context of RSV infection and represents a potential novel pharmacological approach to ameliorate viral-induced lung disease.

Hydrogen Sulfide Attenuates Renin Angiotensin and Aldosterone Pathological Signaling to Preserve Kidney Function and Improve Exercise Tolerance in Heart Failure.

Cardioprotective effects of H2S have been well documented. However, the lack of evidence supporting the benefits afforded by delayed H2S therapy warrants further investigation. Using a murine model of transverse aortic constriction-induced heart failure, this study showed that delayed H2S therapy protects multiple organs including the heart, kidney, and blood-vessel; reduces oxidative stress; attenuates renal sympathetic and renin-angiotensin-aldosterone system pathological activation; and ultimately improves exercise capacity. These findings provide further insights into H2S-mediated cardiovascular protection and implicate the benefits of using H2S-based therapies clinically for the treatment of heart failure.

Phosphonothioate-Based Hydrogen Sulfide Releasing Reagents: Chemistry and Biological Applications.

Hydrogen sulfide (H2S) is a newly recognized gasotransmitter. Studies have demonstrated that the production of endogenous H2S and the exogenous administration of H2S can regulate many physiological and/or pathological processes. Therefore, H2S releasing agents (also known as H2S donors) are important research tools in advancing our understanding of the biology and clinical potential of H2S. Among currently available donors, GYY4137 is probably the most well-known and has been used in many studies in the past 10 years. Recently, a number of GYY4137 derivatives (e.g., phosphonothioate-based compounds) have been developed as H2S donors. In this review, we summarize the development and application of these donors, which include Lawesson's reagent, substituted phosphorodithioates, cyclic phosphorane analogs, and pH-controlled phosphonamidothioates (JK donors). These donors have advantages such as good water-solubility, slow and controllable H2S release capability, and a variety of reported biological activities. However, it should be noted that the detailed H2S release profiles and byproducts under real biological systems are still unclear for many of these donors. Only after we figure out these unknowns we will see better applications of these donors in H2S research and therapy.

Novel H2S Releasing Nanofibrous Coating for In Vivo Dermal Wound Regeneration.

Hydrogen sulfide (H2S), together with nitric oxide and carbon monoxide, has been recognized as an important gasotransmitter. It plays an essential physiological role in regulating cyto-protective signal process, and H2S-based therapy is considered as the next generation of promising therapeutic strategies for many biomedical applications, such as the treatment of cardiovascular disease. Through electrospinning of polycaprolactone (PCL) containing JK1, a novel pH-controllable H2S donor, nanofibers with H2S releasing function, PCL-JK1, are fabricated. This fibrous scaffold showed a pH-dependent H2S releasing behavior, i.e., lower pH induced greater and faster H2S release. In addition, the H2S release of JK1 was prolonged by the fibrous matrix as shown by decreased releasing rates compared to JK1 in solutions. In addition, in vitro studies indicated that PCL-JK1 exhibited excellent cyto-compatibility, similar to PCL fibers. Finally, we investigated PCL-JK1 as a wound dressing toward a cutaneous wound model in vivo and found that PCL-JK1 could significantly enhance the wound repair and regeneration compared with the control PCL scaffold, likely due to the release of H2S, which results in a broad range of physiologically protective functions toward the wound.

Design, Synthesis, and Cardioprotective Effects of N-Mercapto-Based Hydrogen Sulfide Donors.

Hydrogen sulfide (H2S) is a signaling molecule which plays regulatory roles in many physiological and/or pathological processes. Therefore, regulation of H2S levels could have great potential therapeutic value. In this work, we report the design, synthesis, and evaluation of a class of N-mercapto (N-SH)-based H2S donors. Thirty-three donors were synthesized and tested. Our results indicated that controllable H2S release from these donors could be achieved upon structural modifications. Selected donors (NSHD-1, NSHD-2, and NSHD-6) were tested in cellular models of oxidative damage and showed significant cytoprotective effects. Moreover, NSHD-1 and NSHD-2 were also found to exhibit potent protective effects in a murine model of myocardial ischemia reperfusion (MI/R) injury.

Thiol-activated gem-dithiols: a new class of controllable hydrogen sulfide donors.

A class of novel thiol-activated H2S donors has been developed on the basis of the gem-dithiol template. These donors release H2S in the presence of cysteine or GSH in aqueous solutions as well as in cellular environments.