Nitric Oxide Donor-Based Cancer Therapy: Advances and Prospects

Supramolecular red-light-photosensitized nitric oxide release with fluorescence self-reporting within biocompatible nanocarriers

The strict dependence of the biological effects of nitric oxide (NO) on its concentration and generation site requires this inorganic free radical to be delivered with precise spatiotemporal control. Light-activation by suitable NO photoprecursors represents an ideal approach. Developing strategies to activate NO release using long-wavelength excitation light in the therapeutic window (650-1300 nm) is challenging. In this contribution, we demonstrate that NO release by a blue-light activatable NO photodonor (NOPD) with self-fluorescence reporting can be triggered catalytically by the much more biocompatible red light exploiting a supramolecular photosensitization process. Different red-light absorbing photosensitizers (PSs) are co-entrapped with the NOPD within different biocompatible nanocarriers such as Pluronic® micelles, microemulsions and branched cyclodextrin polymers. The intra-carrier photosensitized NO release, involving the lowest, long-lived triplet state of the PS as the key intermediate and its quenching by the NOPD, is competitive with that by molecular oxygen. This allows NO to be released with good efficacy, even under aerobic conditions. Therefore, the adopted general strategy provides a valuable tool for generating NO from an already available NOPD, otherwise activatable with the poorly biocompatible blue light, without requiring any chemical modification and using sophisticated and expensive irradiation sources.

Silver-Catalyzed Decarboxylative Nitrooxylation of Aliphatic Carboxylic Acids

Here, we present a silver-catalyzed decarboxylative nitrooxylation via a radical-based approach. The substrate scope of this reaction prototype extends to nonactivated primary and secondary carboxylic acids. This protocol provides a practical method for the synthesis of an unprecedented family of organic nitrates and exhibits wide functional group compatibility. Preliminary mechanistic studies reveal that a high-valent silver(II) nitrate complex is a versatile NO3 resource pool, allowing for facile C-O bond formation.

The potential of vascular normalization for sensitization to radiotherapy

Radiotherapy causes apoptosis mainly through direct or indirect damage to DNA via ionizing radiation, leading to DNA strand breaks. However, the efficacy of radiotherapy is attenuated in malignant tumor microenvironment (TME), such as hypoxia. Tumor vasculature, due to the imbalance of various angiogenic and anti-angiogenic factors, leads to irregular morphology of tumor neovasculature, disordered arrangement of endothelial cells, and too little peripheral coverage. This ultimately leads to a TME characterized by hypoxia, low pH and high interstitial pressure. This deleterious TME further exacerbates the adverse effects of tumor neovascularization and weakens the efficacy of conventional radiotherapy. Whereas normalization of blood vessels improves TME and thus the efficacy of radiotherapy. In addition to describing the research progress of radiotherapy sensitization and vascular normalization, this review focuses on the strategy and application prospect of modulating vascular normalization to improve the efficacy of radiotherapy sensitization.

Environmentally responsive hydrogel promotes vascular normalization to enhance STING anti-tumor immunity

The immunosuppressive microenvironment of malignant tumors severely hampers the effectiveness of anti-tumor therapy. Moreover, abnormal tumor vasculature interacts with immune cells, forming a vicious cycle that further interferes with anti-tumor immunity and promotes tumor progression. Our pre-basic found excellent anti-tumor effects of c-di-AMP and RRx-001, respectively, and we further explored whether they could be combined synergistically for anti-tumor immunotherapy. We chose to load these two drugs on PVA-TSPBA hydrogel scaffolds that expressly release drugs within the tumor microenvironment by in situ injection. Studies have shown that c-di-AMP activates the STING pathway, enhances immune cell infiltration, and reverses tumor immunosuppression. Meanwhile, RRx-001 releases nitric oxide, which increases oxidative stress injury in tumor cells and promotes apoptosis. Moreover, the combination of the two presented more powerful pro-vascular normalization and reversed tumor immunosuppression than the drug alone. This study demonstrates a new design option for anti-tumor combination therapy and the potential of tumor environmentally responsive hydrogel scaffolds in combination with anti-tumor immunotherapy.

Design, synthesis, and biological studies of nitric oxide-donating piperlongumine derivatives triggered by lysyl oxidase as anti-triple negative breast cancer agents

Nitric oxide (NO) is an important gas messenger molecule with a wide range of biological functions. High concentration of NO exerts promising antitumor effects and is regarded as one of the hot spots in cancer research, that have limitations in their direct application due to its gaseous state, short half-life (seconds) and high reactivity. Lysyl oxidase (LOX) is a copper-dependent amine oxidase that is responsible for the covalent bonding between collagen and elastin and promotes tumor cell invasion and metastasis. The overexpression of LOX in triple-negative breast cancer (TNBC) makes it an attractive target for TNBC therapy. Herein, novel NO donor prodrug molecules were designed and synthesized based on the naturally derived piperlongumine (PL) skeleton, which can be selectively activated by LOX to release high concentrations of NO and PL derivatives, both of them play a synergistic role in TNBC therapy. Among them, the compound TM-1 selectively released NO in highly invasive TNBC cells (MDA-MB-231), and TM-1 was also confirmed as a potential TNBC cell line inhibitor with an inhibitory concentration of 2.274 μM. Molecular docking results showed that TM-1 had a strong and selective binding affinity with LOX protein.

An updated review of the pharmacological effects and potential mechanisms of hederagenin and its derivatives

Hederagenin (HG) is a natural pentacyclic triterpenoid that can be isolated from various medicinal herbs. By modifying the structure of HG, multiple derivatives with superior biological activities and safety profiles have been designed and synthesized. Accumulating evidence has demonstrated that HG and its derivatives display multiple pharmacological activities against cancers, inflammatory diseases, infectious diseases, metabolic diseases, fibrotic diseases, cerebrovascular and neurodegenerative diseases, and depression. Previous studies have confirmed that HG and its derivatives combat cancer by exerting cytotoxicity, inhibiting proliferation, inducing apoptosis, modulating autophagy, and reversing chemotherapy resistance in cancer cells, and the action targets involved mainly include STAT3, Aurora B, KIF7, PI3K/AKT, NF-κB, Nrf2/ARE, Drp1, and P-gp. In addition, HG and its derivatives antagonize inflammation through inhibiting the production and release of pro-inflammatory cytokines and inflammatory mediators by regulating inflammation-related pathways and targets, such as NF-κB, MAPK, JAK2/STAT3, Keap1-Nrf2/HO-1, and LncRNA A33/Axin2/β-catenin. Moreover, anti-pathogen, anti-metabolic disorder, anti-fibrosis, neuroprotection, and anti-depression mechanisms of HG and its derivatives have been partially elucidated. The diverse pharmacological properties of HG and its derivatives hold significant implications for future research and development of new drugs derived from HG, which can lead to improved effectiveness and safety profiles.

Hyaluronic Acid-Coated Silica Nanoparticles for Targeted Delivery of Nitric Oxide to Cancer Cells

Drug resistance and off-target toxicity are two of the greatest challenges to chemotherapeutic melanoma treatments. Nitric oxide (NO) represents an attractive alternative to conventional therapeutics due to its numerous anticancer properties and low probability of engendering resistance. As NO is highly reactive, macromolecular NO donors are needed for the controlled and targeted delivery of NO for therapeutic applications. Herein, mesoporous silica nanoparticles (MSNs) coated with hyaluronic acid (HA) were developed as a NO delivery system to facilitate controlled delivery to cancer cells through both passive and active targeting via the enhanced permeation and retention effect and directed binding of HA with CD44 receptors, respectively. The aminosilane modification, HA concentration, and HA molecular weight were systematically evaluated to facilitate the MSN coating and NO loading. The hydrodynamic diameter and dispersity of the nanoparticles increased after HA coating due to the hydrophilic nature of HA, with greater increases observed at higher HA molecular weight. Lower starting concentrations of HA and aminosilanes with longer alkyl chains favored more efficient HA coating. Faster NO-release kinetics and lower NO payloads were observed for the HA-coated MSNs relative to uncoated MSNs. However, the localized delivery of NO to cancer cells through the active targeting conferred by HA increased levels of oxidative stress and induced mitochondria-mediated apoptosis in melanoma cells. Cytotoxicity was also evaluated against human dermal fibroblasts, with the use of 6 kDa HA-coated MSNs resulting in the greatest therapeutic indices. Enhanced internalization of HA-coated nanoparticles into melanoma cells versus uncoated nanoparticles was visualized with confocal microscopy and quantified by fluorescence spectroscopy. In total, HA-coated MSNs represent a promising NO delivery system for potential use as a chemotherapeutic for skin melanomas.

Stepwise Nitric Oxide Release and Antibacterial Activity of a Nitric Oxide Photodonor Hosted within Cyclodextrin Branched Polymer Nanocarriers

A hydrophobic nitric oxide (NO) photodonor integrating both nitroso and nitro functionalities within its chromophoric skeleton has been synthesized. Excitation of this compound with blue light triggers the release of two NO molecules from the nitroso and the nitro functionalities via a stepwise mechanism. Encapsulation of the NO photodonor within biocompatible neutral, cationic, and anionic β-cyclodextrin branched polymers as suitable carriers leads to supramolecular nanoassemblies, which exhibit the same nature of the photochemical processes but NO photorelease performances enhanced by about 1 order of magnitude when compared with the free guest. Antibacterial tests carried out with methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii demonstrate an effective antibacterial activity exclusively under light activation and point out a differentiated role of the polymeric nanocarriers in determining the outcome of the antibacterial photodynamic action.

All-in-one polysaccharide hydrogel with resistant vascular burst pressure and cooperative wound microenvironment regulation for fatal arterial hemorrhage and diabetic wound healing

Fatal massive hemorrhage and diabetic wound healing are world widely challenging in surgical managements, and uncontrolled bleeding, chronic inflammation and damaged remodeling heavily hinder the whole healing processes. Considering hemostasis, inflammation and wound microenvironment cooperatively affect the healing progression, we design all-in-one beta-glucan (BG) hybrid hydrogels reinforced with laponite nanoclay that demonstrate tunable tissue adhesion, resistant vascular burst pressure and cooperative wound microenvironment regulation for arterial hemostasis and diabetic wound prohealing. Those hydrogels had honeycomb-like porous microstructure with average pore size of 7-19 μm, tissue adhesion strength of 18-46 kPa, and vascular burst pressure of 58-174 mmHg to achieve superior hemostasis in rat liver and femoral artery models. They could effectively scavenge reactive oxygen species, transform macrophages from proinflammatory M1 into prohealing M2, and shorten the inflammation duration via synergistic actions of BG and nitric oxide (NO). Single treatment of NO-releasing BG hybrid hydrogels attained complete closure of diabetic wounds within 14 days, orchestrated to accelerate the epithelization and dermis growth, and restored normal vascularization, achieving high performance healing with optimal collagen deposition and hair follicle regeneration. Consequently, this work opens up a new avenue to design all-in-one polysaccharide hydrogels for applications in massive bleeding hemostats and diabetic wound dressings.

A fluorescent probe with an ultra-rapid response to nitric oxide

Nitric oxide (NO) is a diatomic inorganic free radical ubiquitous in mammalian tissues and cells that plays a multifaceted role in a variety of physiological and pathophysiological processes. The strict dependence of the biological effects of NO on its concentration makes its real-time monitoring crucial. In view of the reactivity of NO with multiple bio-targets, the development of NO sensors that associate a fast response rate with selectivity and sensitivity is very challenging. Herein we report a fluorescent NO probe based on a BODIPY fluorogenic unit covalently linked to a trimethoxy aniline derivative through a flexible spacer. NO leads to effective nitrosation of the highly electron-rich amino active site of the probe through the secondary oxide N2O3, resulting in an increase of BODIPY fluorescence quantum yield from Φf = 0.06 to Φf = 0.55, accompanied by significant changes in the relative amplitude of the fluorescence lifetimes. In situ generation of NO, achieved by a tailored light-activatable NO releaser, allows the real-time detection of NO as a function of its concentration and permits demonstrating that the probe exhibits a very fast response time, being ≤0.1 s. This remarkable data combines with the high sensitivity of the probe to NO (LOD = 35 nM), responsiveness also to ONOO-, the other important secondary oxide of NO, independence from the fluorescence response within a wide pH range, good selectivity towards different analytes and small interference by typical physiological concentrations of glutathione. Validation of this probe in melanoma cell lines is also reported.

Design and Application of an In Situ Traceable Nitric Oxide Donor for Promoting the Healing of Wound Infections

Therapies for wound infections require medications with antibacterial and wound-healing functions. However, it remains a challenge to produce a single drug that can perform dual functions. Nitric oxide (NO), with its antibacterial and wound-healing activities, is an ideal solution to address this challenge. However, many controlled-release strategies for NO rely on external probes for tracing the release in situ, making it difficult to precisely assess the location and magnitude. To address this issue, this study describes a novel NO donor, DHU-NO1, capable of efficiently releasing NO under mild conditions (450 nm illumination). Simultaneously, DHU-NO1 generates the fluorophore Azure B (AZB), which enables direct, non-consumptive tracing of the NO release by monitoring the fluorescence and absorption changes in AZB. Given that NO can be conveniently traced, the amount of released NO can be controlled during biological applications, thereby allowing both functions of NO to be performed. When applied to the affected area, DHU-NO1, illuminated by both a simple light-emitting diode (LED) light source and natural light, achieves significant antibacterial effects against wound infections and promotes wound healing in mice. This study offers a novel and effective approach for treating wound infections.

Targeting epidermal growth factor receptor and its downstream signaling pathways by natural products: A mechanistic insight

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase (RTK) that maintains normal tissues and cell signaling pathways. EGFR is overactivated and overexpressed in many malignancies, including breast, lung, pancreatic, and kidney. Further, the EGFR gene mutations and protein overexpression activate downstream signaling pathways in cancerous cells, stimulating the growth, survival, resistance to apoptosis, and progression of tumors. Anti-EGFR therapy is the potential approach for treating malignancies and has demonstrated clinical success in treating specific cancers. The recent report suggests most of the clinically used EGFR tyrosine kinase inhibitors developed resistance to the cancer cells. This perspective provides a brief overview of EGFR and its implications in cancer. We have summarized natural products-derived anticancer compounds with the mechanistic basis of tumor inhibition via the EGFR pathway. We propose that developing natural lead molecules into new anticancer agents has a bright future after clinical investigation.

Mitochondrial Targeted Thermosensitive Nanocarrier for Near-Infrared-Triggered Precise Synergetic Photothermal Nitric Oxide Chemotherapy

Nitric oxide (NO) intervenes, that is, a potential treatment strategy, and has attracted wide attention in the field of tumor therapy. However, the therapeutic effect of NO is still poor, due to its short half-life and instability. Therapeutic concentration ranges of NO should be delivered to the target tissue sites, cell, and even subcellular organelles and to control NO generation. Mitochondria have been considered a major target in cancer therapy for their essential roles in cancer cell metabolism and apoptosis. In this study, mesoporous silicon-coated gold nanorods encapsulated with a mitochondria targeted and the thermosensitive lipid layer (AuNR@MSN-lipid-DOX) served as the carrier to load NO prodrug (BNN6) to build the near-infrared-triggered synergetic photothermal NO-chemotherapy platform (AuNR@MSN(BNN6)-lipid-DOX). The core of AuNR@MSN exhibited excellent photothermal conversion capability and high loading efficiency in terms of BNN6, reaching a high value of 220 mg/g (w/w), which achieved near-infrared-triggered precise release of NO. The outer biocompatible lipid layer, comprising thermosensitive phospholipid DPPC and mitochondrial-targeted DSPE-PEG2000-DOX, guided the whole nanoparticle to the mitochondria of 4T1 cells observed through confocal microscopy. In the mitochondria, the nanoparticles increased the local temperature over 42 °C under NIR irradiation, and a high NO concentration from BNN6 detected by the NO probe and DSPE-PEG2000-DOX significantly inhibited 4T1 cancer cells in vitro and in vivo under the synergetic photothermal therapy (PTT)-NO therapy-chemotherapy modes. The built NIR-triggered combination therapy nanoplatform can serve as a strategy for multimodal collaboration.

Bifunctional Sildenafil Diazeniumdiolates Acting as Phosphodiesterase 5 Inhibitors and Nitric Oxide Donors- Towards Wound Healing

Inefficient wound healing poses a global health challenge with a lack of efficient treatments. Wound healing issues often correlate with low endogenous nitric oxide (NO) levels. While exogenous delivery with NO-releasing compounds represents a promising therapeutic strategy, controlling the release of the highly reactive NO remains challenging. Phosphodiesterase 5 (PDE5) inhibitors, like sildenafil, have also been shown to promote wound healing. This study explores hybrid compounds, combining NO-releasing diazeniumdiolates with a sildenafil-derived PDE5 inhibitor. One compound demonstrated a favorable NO-release profile, triggered by an esterase (prodrug), and displayed in vitro nanomolar inhibition potency against PDE5 and thrombin-induced platelet aggregation. Both factors are known to promote blood flow and oxygenation. Thus, our findings unveil promising prospects for effective wound healing treatments.

Exploring acetaminophen prodrugs and hybrids: a review

This critical review highlights the advances in developing new molecules for treating pain syndrome, an important issue for human health. Acetaminophen (APAP, known as paracetamol) and nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in clinical practice despite their adverse effects. Research is being conducted to develop innovative drugs with improved pharmaceutical properties to mitigate these effects. A more practical way to achieve that is to study well-known and time-tested drugs in their molecular combinations. Accordingly, the present work explores APAP and their combined chemical entities, i.e., prodrugs (soft drugs), codrugs (mutual prodrugs), and hybrids. Due to their molecular structure, APAP prodrugs or codrugs could be considered merged or conjugated hybrids; all these names are very fluid terms. This article proposed a structural classification of these entities to better analyze their advances. So, the following: carrier-linked O-modified APAP, -linked N-modified APAP derivatives (prodrugs), and direct- and spacer-N,O-linked APAP hybrids (codrugs) are the central parts of this review and are examined, especially ester and amide NSAID-APAP molecules. The C-linked APAP and nitric oxide (NO)-releasing APAP hybrids were also briefly discussed. Prime examples of APAP-based drugs such as propacetamol, benorylate, acetaminosalol, nitroparacetamol, and agent JNJ-10450232 weave well into this classification. The proposed classification is the first and original, giving a better understanding of the SAR studies for new pain relievers research and the design development for the analgesic APAP-(or NSAID)-based compounds.

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Organic nanomotors: emerging versatile nanobots

Artificial nanomotors are self-propelled nanometer-scaled machines that are capable of converting external energy into mechanical motion. A significant progress on artificial nanomotors over the last decades has unlocked the potential of carrying out manipulatable transport and cargo delivery missions with enhanced efficiencies owing to their stimulus-responsive autonomous movement in various complex environments, allowing for future advances in a large range of applications. Emergent kinetic systems with programmable energy-converting mechanisms that are capable of powering the nanomotors are attracting increasing attention. This review highlights the most-recent representative examples of synthetic organic nanomotors having self-propelled motion exclusively powered by organic molecule- or their aggregate-based kinetic systems. The stimulus-responsive propulsion mechanism, motion behaviors, and performance in antitumor therapy of organic nanomotors developed so far are illustrated. A future perspective on the development of organic nanomotors is also proposed. With continuous innovation, it is believed that the scope and possible achievements in practical applications of organic nanomotors with diversified organic kinetic systems will expand.

Red cell membrane-coating Prussian blue for combined photothermal and NO gas therapy for nasopharyngeal carcinoma

Nitric oxide (NO) gas molecules have demonstrated remarkable anti-tumor effects and minimal susceptibility to drug resistance, establishing as a promising modality for effective tumor treatment. However, how to realize its stable and efficient delivery in vivo is still a challenge. In this study, we have developed a heat-responsive biomimetic nano erythrocyte (M/B@R) by loading a NO donor (BNN6) onto mesoporous Prussian blue (M-PB) and subsequently enveloping them with red blood cell membranes. The preserved integrity of the red blood cell membrane (RBCm) structure could ensure its excellent biosafety, prolong its circulation time within the bloodstream and then enhance the accumulation of BNN6 at tumor sites. When M/B@R is stimulated by near-infrared light (NIR-II, 808 nm) irradiation, the nanoparticle could generate significant heat for photothermal therapy (PTT) by the characteristic NIR absorption of M-PB and then NO could also be efficiently released. The generated NO further facilitates the formation of ONOO-, a highly toxic species to tumors, while also alleviating tumor hypoxia. Remarkably, M/B@R, with NIR as the excitation source, induces combined lethality through hyperthermia, DNA damage, and tumor hypoxia relief. This novel combination strategy provides a new avenue for PTT/NO-induced cancer therapy.

Development of Integrated Bioorthogonal Self-Catalyzed NO Donor/Platinum(IV) Prodrugs for Synergistical Intervention against Triple-Negative Breast Cancer

The platinum(IV) prodrug strategy is attractive for the synergistic antitumor effect. High levels (>400 nM) of nitric oxide (NO) exert promising cancer inhibition effects via multiple mechanisms. Herein, we designed and synthesized a new group of integrated bioorthogonal self-catalyzed NO donor/Pt(IV) prodrugs bearing long alkyl chains to enhance the stability in circulation, while the cytoplasmic reductants trigger cascade activation to release Pt and NO in tumor cells. Specifically, compound 10c exhibited an improved stability, favorable pharmacokinetic properties (AUC(0-t) of 2210.10 h*ng/mL), potent anti-triple-negative breast cancer (TNBC) effects (71.08% tumor growth inhibition (TGI) against the MDA-MB-231 xenograft model), potent in vivo anti-TNBC lung metastasis activity, and acceptable low toxicity. Importantly, NO released from 10c leads to the S-nitrosation of metal transporters Atox1&ATP7a in TNBC cells, which increases the Pt retention and inhibits lysyl oxidase, generating synergistic tumoricidal and antimetastatic activity. These results may inspire further study on the synergistical therapy of Pt and NO for the treatment of TNBC.

Chemical Strategies Toward Prodrugs and Fluorescent Probes for Gasotransmitters

Three gaseous molecules are widely accepted as important gasotransmitters in mammalian cells, namely NO, CO and H2S. Due to the pharmacological effects observed in preclinical studies, these three gasotransmitters represent promising drug candidates for clinical translation. Fluorescent probes of the gasotransmitters are also in high demand; however, the mechanisms of actions or the roles played by gasotransmitters under both physiological and pathological conditions remain to be answered. In order to bring these challenges to the attention of both chemists and biologists working in this field, we herein summarize the chemical strategies used for the design of both probes and prodrugs of these three gasotransmitters.

Advances in nitric oxide regulators for the treatment of ischemic stroke

Ischemic stroke (IS) is a life-threatening disease worldwide. Nitric oxide (NO) derived from l-arginine catalyzed by NO synthase (NOS) is closely associated with IS. Three isomers of NOS (nNOS, eNOS and iNOS) produce different concentrations of NO, resulting in quite unlike effects during IS. Of them, n/iNOSs generate high levels of NO, detrimental to brain by causing nerve cell apoptosis and/or necrosis, whereas eNOS releases small amounts of NO, beneficial to the brain via increasing cerebral blood flow and improving nerve function. As a result, a large variety of NO regulators (NO donors or n/iNOS inhibitors) have been developed for fighting IS. Regrettably, up to now, no review systematically introduces the progresses in this area. This article first outlines dynamic variation rule of NOS/NO in IS, subsequently highlights advances in NO regulators against IS, and finally presents perspectives based on concentration-, site- and timing-effects of NO production to promote this field forward.

Development of novel quinoline-NO donor hybrids inducing human breast cancer cells apoptosis via inhibition of topoisomerase I

A number of NO-releasing quinoline derivatives have been designed and synthesized by introducing NO donor to quinoline carboxylic acid fragment. The anti-proliferation of all target compounds was evaluated against human cancer cell lines (HCT-116, MCF-7, and A549), MCF-7/ADR and normal cell (MCF-10A). Most compounds showed cytotoxic activity on cancer cells and drug-resistant cells with IC50 values in the range of 0.62-5.51 μM. Importantly, these compounds showed low toxicity to normal cells (4.21-34.08 μM). Further mechanism studies showed that the most potent compound 9 could release high concentration of NO and inhibit the activity of topoisomerase I. In addition, 9 regulated apoptosis-related proteins, generated ROS and blocked MCF-7 cells in G2/M phase to induce cell apoptosis. Furthermore, the P-gp-mediated transport was also influenced by 9. And 9 could significantly inhibit the growth of tumor in vivo without observable organ-related toxicities. Overall, as a novel NO-releasing quinoline derivative, 9 was worthy for further in-depth study.

Discovery of Efficient Hypoxia-Targeted NO Donor Compounds to Alleviate Hypoxia Cardiac Disease

In order to obtain efficient NO donor drugs to treat hypoxic cardiac disease, a series of hypoxia-targeted NO donor compounds were prepared and screened. Among them, a representative compound H3 was found to selectively release NO under hypoxia with a higher ratio than isosorbide dinitrate (ISDN). In vitro study indicated that H3 had a strong capability of alleviating vascular dilation and reducing myocardial hypoxic injury due to its effective regulation of vascular dilatation and myocardial injury-related proteins in H9c2 cells even at low concentrations. By intraperitoneal injection or intragastric administration, in vivo animal tests revealed that H3 possessed a potent antimyocardial hypoxic injury effect superior to ISDN. These findings suggest that H3 has a better effect on alleviating hypoxic cardiac disease than the conventional drug, owing to its hypoxia-targeted release of NO.

Discovery and bioassay of disubstituted β-elemene-NO donor conjugates: synergistic enhancement in the treatment of leukemia

Natural products are essential sources of antitumor drugs. One such molecule, β-elemene, is a potent antitumor compound extracted from Curcuma wenyujin. In the present investigation, a series of novel 13,14-disubstituted nitric oxide (NO)-donor β-elemene derivatives were designed, with β-elemene as the foundational compound, and subsequently synthesized to evaluate their therapeutic potential against leukemia. Notably, the derivative labeled as compound 13d demonstrated a potent anti-proliferative activity against the K562 cell line, with a high NO release. In vivo studies indicated that compound 13d could effectively inhibit tumor growth, exhibiting no discernible toxic manifestations. Specifically, a significant tumor growth inhibition rate of 62.9% was observed in the K562 xenograft tumor mouse model. The accumulated data propound the potential therapeutic application of compound 13d in the management of leukemia.

A review of progress in o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities for cancer therapy

Histone deacetylases, as a new class of anticancer targets, could maintain homeostasis by catalyzing histone deacetylation and play important roles in regulating the expression of target genes. Due to the fact that simultaneous intervention with dual tumor related targets could improve treatment effects, researches on innovative design of dual-target drugs are underway. HDAC is known as a "sensitizer" for the synergistic effects with other anticancer-target drugs because of its flexible structure design. The synergistic effects of HDAC inhibitor and other target inhibitors usually show enhanced inhibitory effects on tumor cells, and also provide new strategies to overcome multidrug resistance. Many research groups have reported that simultaneously inhibiting HDAC and other targets, such as tubulin, EGFR, could enhance the therapeutic effects. The o-aminobenzamide group is often used as a ZBG group in the design of HDAC inhibitors with potent antitumor effects. Given the prolonged inhibitory effects and reduced toxic side effects of HDAC inhibitors using o-aminobenzamide as the ZBG group, the o-aminobenzamide group is expected to become a more promising alternative to hydroxamic acid. In fact, o-aminobenzamide-based dual inhibitors of HDAC with different chemical structures have been extensively prepared and reported with synergistic and enhanced anti-tumor effects. In this work, we first time reviewed the rational design, molecular docking, inhibitory activities and potential application of o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities in cancer therapy, which might provide a reference for developing new and more effective anticancer drugs.

Cancer Resistance Is Mediated by the Upregulation of Several Anti-Apoptotic Gene Products via the Inducible Nitric Oxide Synthase/Nitric Oxide Pathway: Therapeutic Implications

Significance: Several therapeutic strategies for cancer treatments have been developed with time, and significant milestones have been achieved recently. However, with these novel therapies, not all cancer types respond and in the responding cancer types only a subset is affected. The failure to respond is principally the result that these cancers develop several mechanisms of resistance. Thus, a focus of current research investigations is to unravel the various mechanisms that regulate resistance and identify suitable targets for new therapeutics. Recent Advances: Hence, many human cancer types have been reported to overexpress the inducible nitric oxide synthase (iNOS) and it has been suggested that iNOS/nitric oxide (NO) plays a pivotal role in the regulation of resistance. We have postulated that iNOS overexpression or NO regulates the overexpression of pivotal anti-apoptotic gene products such as B-cell lymphoma 2 (Bcl-2), B-cell lymphoma extra large (Bcl-xL), myeloid cell leukemia-1 (Mcl-1), and survivin. In this report, we describe the various mechanisms, transcriptional, post-transcriptional, and post-translational, by which iNOS/NO regulates the expression of the above anti-apoptotic gene products. Critical Issues: The iNOS/NO-mediated regulation of the four gene products is not the same with both specific and overlapping pathways. Our findings are, in large part, validated by bioinformatic analyses demonstrating, in several cancers, several direct correlations between the expression of iNOS and each of the four examined anti-apoptotic gene products. Future Directions: We have proposed that targeting iNOS may be highly efficient since it will result in the underexpression of multiple anti-apoptotic proteins and shifting the balance toward the proapoptotic gene products and reversal of resistance. Antioxid. Redox Signal. 39, 853-889.

Novel Nitric Oxide Donor-Azole Conjugation Strategy for Efficient Treatment of Cryptococcus neoformans Infections

Invasive fungal infections (IFIs) such as cryptococcal meningitis (CM) remain a serious health issue worldwide due to drug resistance closely related to biofilm formation. Unfortunately, available antifungal drugs with ideal safety and promising potency are still lacking; thus, the research of new candidate and therapeutic approach is urgently needed. As an important gas messenger molecule, nitric oxide (NO) shows vital inhibition on various microorganism biofilms. Hence, three series of novel NO-donating azole derivatives were designed and synthesized, and the in vitro antifungal activity as well as the mechanism of action was investigated. Among them, 3a and 3e displayed excellent antifungal activity against Cryptococcus neoformans and biofilm depending on the release of NO. Moreover, a more stable analogue 3h of 3a demonstrated markedly anti-CM effects via intranasal dropping, avoiding the first-pass effects and possessing a better brain permeability bypass blood-brain barrier. These results present a promising antifungal candidate and intranasal dropping approach for the treatment of CM, warranting further studies.

Regioselective Synthesis of NO-Donor (4-Nitro-1,2,3-triazolyl)furoxans via Eliminative Azide-Olefin Cycloaddition

A facile and efficient method for the regioselective [3 + 2] cycloaddition of 4-azidofuroxans to 1-dimethylamino-2-nitroethylene under p-TSA catalysis affording (4-nitro-1,2,3-triazolyl)furoxans was developed. This transformation is believed to proceed via eliminative azide-olefin cycloaddition resulting in its complete regioselectivity. The developed protocol has a broad substrate scope and enables a straightforward assembly of the 4-nitro-1,2,3-triazole motif. Moreover, synthesized (4-nitro-1,2,3-triazolyl)furoxans were found to be capable of NO release in a broad range of concentrations, thus providing a novel platform for future drug design and related biomedical applications of heterocyclic NO donors.

Nitric oxide-driven nanotherapeutics for cancer treatment

Nitric oxide (NO) is a gaseous molecule endowed with diverse biological functions, offering vast potential in the realm of cancer treatment. Considerable efforts have been dedicated to NO-based cancer therapy owing to its good biosafety and high antitumor activity, as well as its efficient synergistic therapy with other antitumor modalities. However, delivering this gaseous molecule effectively into tumor tissues poses a significant challenge. To this end, nano drug delivery systems (nano-DDSs) have emerged as promising platforms for in vivo efficient NO delivery, with remarkable achievements in recent years. This review aims to provide a summary of the emerging NO-driven antitumor nanotherapeutics. Firstly, the antitumor mechanism and related clinical trials of NO therapy are detailed. Secondly, the latest research developments in the stimulation of endogenous NO synthesis are presented, including the regulation of nitric oxide synthases (NOS) and activation of endogenous NO precursors. Moreover, the emerging nanotherapeutics that rely on tumor-specific delivery of NO donors are outlined. Additionally, NO-driven combined nanotherapeutics for multimodal cancer theranostics are discussed. Finally, the future directions, application prospects, and challenges of NO-driven nanotherapeutics in clinical translation are highlighted.

Design, Synthesis, and Biological Evaluation of Esculetin-Furoxan-DEAC Ternary Hybrids for Anti-Triple Negative Breast Cancer

Twelve new hybrid compounds of Esculetin with nitric oxide (NO) donors and/or mitochondrial targeting groups were designed, synthesized, and evaluated for their anti-tumor activity and mechanism in vitro and in vivo. Notably, the most potent compound A11 exhibited nanomolar antiproliferative activity on triple-negative breast cancer (TNBC) MDA-MB-231 cells (IC50 = 8 nM) with a strikingly selective inhibitory effect. The mechanism of A11 involves targeting MDA-MB-231 cells' mitochondria, releasing a high NO concentration, and increasing the expression of cyclophilin D (CypD), leading to increased reactive oxygen species (ROS) and triggering cancer cell apoptosis. Additionally, A11 could arrest the cell cycle at the G2/M phase to achieve anti-tumor effects. Moreover, A11 demonstrated a superior TNBC inhibition rate and diminished toxicity relative to doxorubicin (DOX) in vivo. In summary, A11 serves as a noteworthy contender for TNBC treatment with high potency and minimal toxicity.

Can Nitric Oxide-Based Therapy Be Improved for the Treatment of Cancers? A Perspective

Since the early observations that nitric oxide (•NO) at high concentrations is cytotoxic to cancer cells and that it may play an important role in the treatment of human cancers, a significant number of compounds (NO-donors) have been prepared to deliver •NO to tumors. •NO also sensitizes various clinically active anticancer drugs and has been shown to induce the reversal of multi-drug resistance in tumor cells expressing ATP-binding cassette-transporter proteins. For the successful treatment of cancers, •NO needs to be delivered precisely to tumors, and its adverse toxicity must be limited. Like other chemotherapeutics, the precise delivery of drugs has been a problem and various attempts have been made, such as the encapsulation of drugs in lipid polymers, to overcome this. This prospective study examines the use of various strategies for delivering •NO (using NO-donors) for the treatment of cancers. Finding and utilizing such a delivery system is an important step in delivering cytotoxic concentrations of •NO to tumors without adverse reactions, leading to a successful clinical outcome for patient management.

Bj-PRO-10c, as an allosteric regulator of argininosuccinate synthase, is a potential therapy for neuroblastoma metastasis

Cancer is a global public health issue. Neuroblastoma (NB) originates from any tissue of the sympathetic nervous system, and the most affected site is the abdomen. The adrenal gland is the primary site in 38% of cases. Approximately 50% of patients have metastatic disease at diagnosis, and bone marrow is often affected. Metastatic disease is characterized by the spreading of cancer cells that are frequently resistant to chemotherapy and radiotherapy from the primary tumor to other specific parts of the body and is responsible for 90% of cancer-related deaths. Increasing evidence has indicated that nitric oxide (NO) signaling is implicated in the pathophysiology of many types of cancer, particularly in tumorigenesis and cancer progression. However, the effect of NO on metastasis cannot be easily classified as prometastatic or antimetastatic. An understanding at the molecular level of the role of NO in cancer will have profound therapeutic implications for the diagnosis and treatment of disease. Here, the proline-rich decapeptide isolated from Bothrops jararaca venom (Bj-PRO-10c) that enhances and sustains the generation of NO was used to unravel the role of metabolic NO in steps of metastasis. Bj-PRO-10c showed an antimetastatic effect, mainly by interfering with actin cytoskeleton rearrangement, controlling cell proliferation, and decreasing the seeding efficiency of NB in metastatic niches. Therefore, we proposed that an approach for controlled NO induction with the right molecular strategies can hopefully inhibit metastasis and increase the lifespan of NB patients.

Antioxidant and Prooxidant Nanozymes: From Cellular Redox Regulation to Next-Generation Therapeutics

Nanozymes, nanomaterials with enzyme-mimicking activity, have attracted tremendous interest in recent years owing to their ability to replace natural enzymes in various biomedical applications, such as biosensing, therapeutics, drug delivery, and bioimaging. In particular, the nanozymes capable of regulating the cellular redox status by mimicking the antioxidant enzymes in mammalian cells are of great therapeutic significance in oxidative-stress-mediated disorders. As the distinction of physiological oxidative stress (oxidative eustress) and pathological oxidative stress (oxidative distress) occurs at a fine borderline, it is a great challenge to design nanozymes that can differentially sense the two extremes in cells, tissues and organs and mediate appropriate redox chemical reactions. In this Review, we summarize the advances in the development of redox-active nanozymes and their biomedical applications. We primarily highlight the therapeutic significance of the antioxidant and prooxidant nanozymes in various disease model systems, such as cancer, neurodegeneration, and cardiovascular diseases. The future perspectives of this emerging area of research and the challenges associated with the biomedical applications of nanozymes are described.

Design, synthesis and biological evaluation of nitric oxide-releasing 5-cyano-6-phenyl-2, 4-disubstituted pyrimidine derivatives

In this study, a series of nitric oxide (NO) -releasing 5-cyano-6-phenyl-2, 4-disubstituted pyrimidine derivatives were designed and synthesized. In the in vitro biological evaluation, compound 24l exhibited optimal antiproliferative activity against MGC-803 cells with the IC₅₀ value of 0.95 µM, significantly better than that of the positive control 5-FU. In addition, preliminary mechanistic studies indicated that 24l inhibited colony formation and blocked MGC-803 cells in the G0/G1 phase. DAPI staining, reactive oxygen species and apoptosis assays demonstrated that 24l induced apoptosis of MGC-803 cells. Particularly, the most potent compound 24l produced the highest level of NO, and the antiproliferative activity was significantly reduced after preincubation with NO scavengers. In conclusion, compound 24l may be considered as a potential candidate antitumor agent.

The Effects of Nitric Oxide on Choroidal Gene Expression

Purpose

Nitric oxide (NO) is recognized as an important biological mediator that controls several physiological functions, and evidence is now emerging that this molecule may play a significant role in the postnatal control of ocular growth and myopia development. We therefore sought to understand the role that nitric oxide plays in visually-guided ocular growth in order to gain insight into the underlying mechanisms of this process.

Methods

Choroids were incubated in organ culture in the presence of the NO donor, PAPA-NONOate (1.5 mM). Following RNA extraction, bulk RNA-seq was used to quantify and compare choroidal gene expression in the presence and absence of PAPA-NONOate. We used bioinformatics to identify enriched canonical pathways, predicted diseases and functions, and regulatory effects of NO in the choroid.

Results

Upon treatment of normal chick choroids with the NO donor, PAPA-NONOate, we identified a total of 837 differentially expressed genes (259 upregulated genes, 578 down-regulated genes) compared with untreated controls. Among these, the top five upregulated genes were LSMEM1, STEAP4, HSPB9, and CCL19, and the top five down-regulated genes were CDCA3, SMC2, a novel gene (ENSALGALG00000050836), an uncharacterized gene (LOC107054158), and SPAG5. Bioinformatics predicted that NO treatment will activate pathways involved in cell and organismal death, necrosis, and cardiovascular system development, and inhibit pathways involved in cell proliferation, cell movement, and gene expression.

Conclusions

The findings reported herein may provide insight into possible effects of NO in the choroid during visually regulated eye growth, and help to identify targeted therapies for the treatment of myopia and other ocular diseases.

Research development of porphyrin-based metal-organic frameworks: targeting modalities and cancer therapeutic applications

Porphyrins are naturally occurring organic molecules that have attracted widespread attention for their potential in the field of biomedical research. Porphyrin-based metal-organic frameworks (MOFs) that utilize porphyrin molecules as organic ligands have gained attention from researchers due to their excellent results as photosensitizers in tumor photodynamic therapy (PDT). Additionally, MOFs hold significant promise and potential for other tumor therapeutic approaches due to their tunable size and pore size, excellent porosity, and ultra-high specific surface area. Active delivery of nanomaterials via targeted molecules for tumor therapy has demonstrated greater accumulation, lower drug doses, higher therapeutic efficacy, and reduced side effects relative to passive targeting through the enhanced permeation and retention effect (EPR). This paper presents a comprehensive review of the targeting methods employed by porphyrin-based MOFs in tumor targeting therapy over the past few years. It further discusses the applications of porphyrin-based MOFs for targeted cancer therapy through various therapeutic methods. The objective of this paper is to provide a valuable reference and source of ideas for targeted therapy using porphyrin-based MOF materials and to inspire further exploration of their potential in the field of cancer therapy.

Hyperthermia-triggered NO release based on Cu-doped polypyrrole for synergistic catalytic/gas cancer therapy

Nitric oxide (NO) is a crucial gaseous medium for tumor growth and progression, but it may also cause mitochondrial disorder and DNA damage by drastically increasing its concentration in tumor. Due to its challenging administration and unpredictable release, NO based gas therapy is difficult to eliminate malignant tumor at low safe doses. To address these issues, herein, we develop a multifunctional nanocatalyst called Cu-doped polypyrrole (CuP) as an intelligent nanoplatform (CuP-B@P) to deliver the NO precursor BNN6 and specifically release NO in tumors. Under the aberrant metabolic environment of tumors, CuP-B@P catalyzes the conversion of antioxidant GSH into GSSG and excess H₂O₂ into ·OH through Cu⁺/Cu²⁺ cycle, which results in oxidative damage to tumor cells and the concomitant release of cargo BNN6. More importantly, after laser exposure, nanocatalyst CuP can absorb and convert photons into hyperthermia, which in turn, accelerates the aforesaid catalytic efficiency and pyrolyzes BNN6 into NO. Under the synergistic effect of hyperthermia, oxidative damage, and NO burst, almost complete tumor elimination is achieved in vivo with negligible toxicity to body. Such an ingenious combination of NO prodrug and nanocatalytic medicine provides a new insight into the development of NO based therapeutic strategies. STATEMENT OF SIGNIFICANCE: A hyperthermia-responsive NO delivery nanoplatform (CuP-B@P) based on Cu-doped polypyrrole was designed and fabricated, in which CuP catalyzed the conversion of H₂O₂ and GSH into ·OH and GSSG to induce intratumoral oxidative damage. After laser irradiation, hyperthermia ablation and responsive release of NO further coupled with oxidative damage to eliminate malignant tumors. This versatile nanoplatform provides new insights into the combined application of catalytic medicine and gas therapy.

Advanced Nitric Oxide Generating Nanomedicine for Therapeutic Applications

Nitric oxide (NO), a gaseous transmitter extensively present in the human body, regulates vascular relaxation, immune response, inflammation, neurotransmission, and other crucial functions. Nitrite donors have been used clinically to treat angina, heart failure, pulmonary hypertension, and erectile dysfunction. Based on NO's vast biological functions, it further can treat tumors, bacteria/biofilms and other infections, wound healing, eye diseases, and osteoporosis. However, delivering NO is challenging due to uncontrolled blood circulation release and a half-life of under five seconds. With advanced biotechnology and the development of nanomedicine, NO donors packaged with multifunctional nanocarriers by physically embedding or chemically conjugating have been reported to show improved therapeutic efficacy and reduced side effects. Herein, we review and discuss recent applications of NO nanomedicines, their therapeutic mechanisms, and the challenges of NO nanomedicines for future scientific studies and clinical applications. As NO enables the inhibition of the replication of DNA and RNA in infectious microbes, including COVID-19 coronaviruses and malaria parasites, we highlight the potential of NO nanomedicines for antipandemic efforts. This review aims to provide deep insights and practical hints into design strategies and applications of NO nanomedicines.

Ultrasound-Induced Piezocatalysis Triggered NO Generation for Enhanced Hypoxic Tumor Therapy

Conventional NO gas generation based on l-arginine (l-Arg) is usually dependent on H₂O₂ and O₂, both of which are very limited within the tumor microenvironment, thus greatly limiting l-Arg's therapeutic effect. Herein, a novel nanoplatform for efficiently triggering NO production based on ultrasound-induced piezocatalysis was developed, which was fabricated by coating amphiphilic poly-l-arginine (DSPE-PEG₂₀₀₀-Arg, DPA) on the piezoelectric material of barium titanate (BTO). The resulting BTO@DPA nanoparticles can efficiently generate H₂O₂, ¹O₂, and O₂ via ultrasound-induced piezocatalysis based on BTO and oxidize the surface arginine to produce NO, which can even further interact with the reactive oxygen species (ROS) to produce more reactive peroxynitrite, thus inducing serious tumor cell apoptosis both in hypoxia and normoxia. After intravenous injection, BTO@DPA accumulated well at the tumor tissue at 4 h postinjection; later, ultrasound irradiation on the tumor not only achieved the best tumor inhibition rate of ∼70% but also completely inhibited tumor metastasis to the lungs via the alleviation of tumor hypoxia. Such a strategy was not dependent on the tumor microenvironment and can be well controlled by ultrasound irradiation, providing a simple and efficient therapy paradigm for hypoxic tumor.

Passing of Nanocarriers across the Histohematic Barriers: Current Approaches for Tumor Theranostics

Over the past several decades, nanocarriers have demonstrated diagnostic and therapeutic (i.e., theranostic) potencies in translational oncology, and some agents have been further translated into clinical trials. However, the practical application of nanoparticle-based medicine in living organisms is limited by physiological barriers (blood-tissue barriers), which significantly hampers the transport of nanoparticles from the blood into the tumor tissue. This review focuses on several approaches that facilitate the translocation of nanoparticles across blood-tissue barriers (BTBs) to efficiently accumulate in the tumor. To overcome the challenge of BTBs, several methods have been proposed, including the functionalization of particle surfaces with cell-penetrating peptides (e.g., TAT, SynB1, penetratin, R8, RGD, angiopep-2), which increases the passing of particles across tissue barriers. Another promising strategy could be based either on the application of various chemical agents (e.g., efflux pump inhibitors, disruptors of tight junctions, etc.) or physical methods (e.g., magnetic field, electroporation, photoacoustic cavitation, etc.), which have been shown to further increase the permeability of barriers.

Design, synthesis and evaluation of nitric oxide releasing derivatives of 2,4-diaminopyrimidine as novel FAK inhibitors for intervention of metastatic triple-negative breast cancer

To search for novel medicines for intervention of triple-negative breast cancer (TNBC), a series of phenylsulfonyl furoxan-based 2,4-diaminopyrimidine derivatives (8a-t) were designed and synthesized based on blocking FAK-mediated signaling pathways through both kinase-dependent and -independent manners. The most active compound 8f not only significantly inhibited FAK kinase activity (IC₅₀ = 27.44 nM), displayed potent inhibitory effects on the proliferation (IC₅₀ = 0.126 μM), invasion and migration of MDA-MB-231 cells, superior to the most widely studied FAK inhibitor, TAE226, bearing 2,4-diaminopyrimidine, but also released high levels of NO, contributing to blockage of FAK mediated-signaling pathways by upregulating of p53 as well as suppressing the Y397 phosphorylation and its downstream effectors, including p-Akt, MMP-2, and MMP-9 via kinase-independent manner, leading to apoptosis induction and decrease of FAs and SFs in TNBC cells. Importantly, 8f inhibited the lung metastasis of TNBC in vivo. Together, 8f may serve as a promising candidate for the treatment of metastatic TNBC.

A Review of RRx-001: A Late-Stage Multi-Indication Inhibitor of NLRP3 Activation and Chronic Inflammation

Chronic unresolving inflammation is emerging as a key underlying pathological feature of many if not most diseases ranging from autoimmune conditions to cardiometabolic and neurological disorders. Dysregulated immune and inflammasome activation is thought to be the central driver of unresolving inflammation, which in some ways provides a unified theory of disease pathology and progression. Inflammasomes are a group of large cytosolic protein complexes that, in response to infection- or stress-associated stimuli, oligomerize and assemble to generate a platform for driving inflammation. This occurs through proteolytic activation of caspase-1-mediated inflammatory responses, including cleavage and secretion of the proinflammatory cytokines interleukin (IL)-1β and IL-18, and initiation of pyroptosis, an inflammatory form of cell death. Several inflammasomes have been characterized. The most well-studied is the nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome, so named because the NLRP3 protein in the complex, which is primarily present in immune and inflammatory cells following activation by inflammatory stimuli, belongs to the family of nucleotide-binding and oligomerization domain (Nod) receptor proteins. Several NLRP3 inflammasome inhibitors are in development, all with multi-indication activity. This review discusses the current status, known mechanisms of action, and disease-modifying therapeutic potential of RRx-001, a direct NLRP3 inflammasome inhibitor under investigation in several late-stage anticancer clinical trials, including a phase 3 trial for the treatment of third-line and beyond small cell lung cancer (SCLC), an indication with no treatment, in which RRx-001 is combined with reintroduced chemotherapy from the first line, carboplatin/cisplatin and etoposide (ClinicalTrials.gov Identifier: NCT03699956). Studies from multiple independent groups have now confirmed that RRx-001 is safe and well tolerated in humans. Additionally, emerging evidence in preclinical animal models suggests that RRx-001 could be effective in a wide range of diseases where immune and inflammasome activation drives disease pathology.

Dendritic Plasmonic CuPt Alloys for Closed-Loop Multimode Cancer Therapy with Remarkably Enhanced Efficacy

The outcome of laser-triggered plasmons-induced phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is significantly limited by the hypoxic tumor microenvironment and the upregulation of heat shock proteins (HSPs) in response to heat stress. Mitochondria, the biological battery of cells, can serve as an important breakthrough to overcome these obstacles. Herein, dendritic triangular pyramidal plasmonic CuPt alloys loaded with heat-sensitive NO donor N, N'-di-sec-butyl-N, N'-dinitroso-1,4-phenylenediamine (BNN) is developed. Under 808 nm laser irradiation, plasmonic CuPt can generate superoxide anion free radicals (·O₂ ^- ) and heat simultaneously. The heat generated can then trigger the release of NO gas, which not only enables gas therapy but also damages the mitochondrial respiratory chain. Impaired mitochondrial respiration leads to reduced oxygen consumption and insufficient intracellular ATP supply, which effectively alleviates tumor hypoxia and undermines the synthesis of HSPs, in turn boosting plasmonic CuPt-based PDT and mild PTT. Additionally, the generated NO and ·O₂ ^- can react to form more cytotoxic peroxynitrite (ONOO^- ). This work describes a plasmonic CuPt@BNN (CPB) triggered closed-loop NO gas, free radicals, and mild photothermal therapy strategy that is highly effective at reciprocally promoting antitumor outcomes.

In Vitro Drug Repurposing: Focus on Vasodilators

Drug repurposing aims to identify new therapeutic uses for drugs that have already been approved for other conditions. This approach can save time and resources compared to traditional drug development, as the safety and efficacy of the repurposed drug have already been established. In the context of cancer, drug repurposing can lead to the discovery of new treatments that can target specific cancer cell lines and improve patient outcomes. Vasodilators are a class of drugs that have been shown to have the potential to influence various types of cancer. These medications work by relaxing the smooth muscle of blood vessels, increasing blood flow to tumors, and improving the delivery of chemotherapy drugs. Additionally, vasodilators have been found to have antiproliferative and proapoptotic effects on cancer cells, making them a promising target for drug repurposing. Research on vasodilators for cancer treatment has already shown promising results in preclinical and clinical studies. However, additionally research is needed to fully understand the mechanisms of action of vasodilators in cancer and determine the optimal dosing and combination therapy for patients. In this review, we aim to explore the molecular mechanisms of action of vasodilators in cancer cell lines and the current state of research on their repurposing as a treatment option. With the goal of minimizing the effort and resources required for traditional drug development, we hope to shed light on the potential of vasodilators as a viable therapeutic strategy for cancer patients.

Heterogeneity of cGMP signalling in tumour cells and the tumour microenvironment: Challenges and chances for cancer pharmacology and therapeutics

The second messenger cyclic guanosine monophosphate (cGMP) is an important regulator of human (patho-)physiology and has emerged as an attractive drug target. Currently, cGMP-elevating drugs are mainly used to treat cardiovascular diseases, but there is also increasing interest in exploring their potential for cancer prevention and therapy. In this review article, we summarise recent findings in cancer-related cGMP research, with a focus on melanoma, breast cancer, colorectal cancer, prostate cancer, glioma, and ovarian cancer. These studies indicate tremendous heterogeneity of cGMP signalling in tumour tissue. It appears that different tumour and stroma cells, and perhaps different sexes, express different cGMP generators, effectors, and degraders. Therefore, the same cGMP-elevating drug can lead to different outcomes in different tumour settings, ranging from inhibition to promotion of tumourigenesis or therapy resistance. These findings, together with recent evidence that increased cGMP signalling is associated with worse prognosis in several human cancers, challenge the traditional view that cGMP elevation generally has an anti-cancer effect. As cGMP pathways appear to be more stable in the stroma than in tumour cells, we suggest that cGMP-modulating drugs should preferentially target the tumour microenvironment. Indeed, there is evidence that phosphodiesterase 5 inhibitors like sildenafil enhance anti-tumour immunity by acting on immune cells. Moreover, many in vivo results obtained with cGMP-modulating drugs could be explained by effects on the tumour vasculature rather than on the tumour cells themselves. We therefore propose a model that incorporates the NO/cGMP signalling pathway in tumour vessels as a key target for cancer therapy. Deciphering the multifaceted roles of cGMP in cancer is not only a challenge for basic research, but also provides a chance to predict potential adverse effects of cGMP-modulating drugs in cancer patients and to develop novel anti-tumour therapies by precision targeting of the relevant cells and molecular pathways.

Nitrate and sodium nitroprusside alter the development of Asian black-spined toads' embryos by inducing nitric oxide production

Nitrate is the most stable and abundant form of inorganic nitrogen in water. However, owing to human activities, the nitrate concentration in aquatic ecosystems has notably increased worldwide. One of the mechanisms underlying nitrate toxicity in vertebrates includes the functional inhibition of the sodium iodide symporter, resulting in thyroid dysfunction. In this study, we aimed to determine the alternative mechanisms underlying the toxicological effects of nitrates on the Asian black-spined toad (Duttaphrynus melanostictus). Embryos of D. melanostictus were exposed to sodium nitroprusside (SNP, positive control) or 100 mg/L nitrate-nitrogen (NO₃-N) for 184 h. We observed that both SNP and NO₃-N significantly decreased body mass and length and delayed developmental processes. Teratogenic symptoms, including tumors, hyperplasia, and abdominal edema, were also observed in embryos exposed to SNP and NO₃-N. Furthermore, SNP and NO₃-N significantly increased nitric oxide levels in the embryos, altering the thyroid hormone, nitrogen, cytochrome P450-mediated drug, and xenobiotic metabolism signaling pathways, as well as the pathway involved in chemical carcinogenesis. The similar toxicological effects of SNP and NO₃-N suggested that nitrate toxicity resulted from the generation of nitric oxide. Therefore, the present study provides insights into an alternative mechanism underpinning nitrate toxicity, which is useful for the conservation of amphibians in nitrate-rich environments.

Pd0 -Catalyzed Asymmetric Carbonitratation Reaction Featuring an H-Bonding-Driven Alkyl-PdII -ONO2 Reductive Elimination

Reductive elimination of alkyl-Pd^II -O is a synthetically useful yet underdeveloped elementary reaction. Here we report that the combination of an H-bonding donor [PyH][BF₄ ] and AgNO₃ additive under toluene/H₂ O biphasic system can enable such elementary step to form alkyl nitrate. This results in the Pd⁰ -catalyzed asymmetric carbonitratations of (Z)-1-iodo-1,6-dienes with (R)-BINAP as the chiral ligand, affording alkyl nitrates up to 96 % ee. Mechanistic studies disclose that the reaction consists of oxidative addition of Pd⁰ catalyst to vinyl iodide, anion ligand exchange between I^- and NO₃ ^- , alkene insertion and S_N 2-type alkyl-Pd^II -ONO₂ reductive elimination. Evidences suggest that H-bonding interaction of PyH⋅⋅⋅ONO₂ can facilitate dissociation of O₂ NO^- ligand from the alkyl-Pd^II -ONO₂ species, thus enabling the challenging alkyl-Pd^II -ONO₂ reductive elimination to be feasible.

Design, synthesis and anti-ovarian cancer activities of thieno[2,3-d]pyrimidine based chimeric BRD4 inhibitor/nitric oxide-donator

Bromodomain protein 4 (BRD4) is an attractive epigenetic target that regulating diverse cellular processes, and the discovery of dual-target inhibitors including BRD4 is an effective approach in cancer treatment to increase potency and reduce drug resistance. Based on the multifunctional drug development strategy, a series of new derivatives of nitrooxy (ONO₂) or furoxan (1,2,5-oxadiazole 2-oxide) with BRD4 inhibitor capable of inhibiting BRD4 and simultaneously releasing NO were designed and synthesized. When NO concentrations were measured with Griess reagent under physiological conditions, all compounds released NO at micromolar levels, reaching effective antitumor concentrations. Biological studies showed that the most potent BRD4/NO hybrid 11a exhibited good BRD4 inhibitory activity and selectivity. Further mechanistic studies revealed that 11a significantly decreased the expression of BRD4 and c-Myc, as well as induced cellular apoptosis and autophagic cell death both in vitro and in vivo. In summary, we optimized the chimeric BRD4-inhibitor/NO-donor based on our previous studies, and it should be a lead compound for targeted therapy of OC (ovarian cancer) in the future. This interesting strategy could expand the usage of BRDi in human malignancies and endogenous gastro-transmitters.

New Nitric Oxide-Releasing Compounds as Promising Anti-Bladder Cancer Drugs

Bladder cancer is a worldwide problem and improved therapies are urgently needed. In the search for newer strong antitumor compounds, herein, we present the study of three nitric oxide-releasing compounds and evaluate them as possible therapies for this malignancy. Bladder cancer cell lines T24 and 253J were used to evaluate the antiproliferative, antimigratory, and genotoxic effects of compounds. Moreover, we determined the NF-κB pathway inhibition, and finally, the survivin downregulation exerted by our molecules. The results revealed that compounds 1 and 3 exerted a high antiproliferative activity against bladder cancer cells through DNA damage and survivin downregulation. In addition, compound 3 reduced bladder cancer cell migration. We found that nitric oxide donors are promising molecules for the development of a new therapeutic targeting the underlying mechanisms of tumorigenesis and progression of bladder cancer.

Single-Component Photo-Responsive Template for the Controlled Release of NO and H2S2

Redox signaling molecules include a number of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS). These molecules work collectively in the regulation of many physiological processes. Understanding the crosstalk mechanisms in these signaling molecules is important but challenging. The development of donor compounds of ROS/RNS/RSS will aid the advances in this field. While many donors that can release one ROS/RNS/RSS have been developed, dual donors that can release two signaling species and facilitate their crosstalk studies are still very rare. Those limited examples lack the ability to precisely control the timing of two releases. In this work, a 2-methoxy-6-naphthacyl-derived tertiary SNO compound, Naph-SNO, was designed and evaluated as the dual donor for NO and H₂S₂. The 2-methoxy-6-naphthacyl structure was demonstrated to be a novel photoremovable protecting group that could directly uncage C-S bonds. Under the irradiation of lights with different wavelengths (visible or UV), Naph-SNO could release NO and H₂S₂ in a stepwise manner, or simultaneously (i.e., likely producing the crosstalk product HSNO/HSSNO). In addition, the release of payloads from the donor also produced an end product with blue fluorescence. Therefore, the release process could be easily monitored in "real time." This controllable photo-triggered release strategy has the potential to be used in the design of other RNS/RSS dual donors.