Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Self-propelling intelligent nanomotor: A dual-action photothermal and starvation strategy for targeted deep tumor destruction

Delivering nanoparticles to deep tumor tissues while maintaining high therapeutic efficacy and minimizing damage to surrounding tissues has long posed a significant challenge. To address this, we have developed innovative self-propelling bowl-shaped nanomotors MSLA@GOx-PDA composed of mesoporous silica loaded with l-arginine and polydopamine, along with glucose oxidase (GOx). These nanomotors facilitate the generation of hydrogen peroxide through GOx-catalyzed glucose oxidation, thereby initiating nitric oxide production from l-arginine. This dual mechanism equips MSLA@GOx-PDA with the robust motility required for deep tumor tissue penetration while depleting essential nutrients necessary for tumor growth, consequently impeding tumor progression. In addition, near-infrared lasers have the significant advantage of being depth-penetrating and non-invasive, allowing real-time fluorescence imaging and guiding dopamine-mediated mild photothermal therapy. Notably, starvation therapy depletes intracellular adenosine triphosphate and inhibits the synthesis of heat shock proteins, thus overcoming the Achilles' heel of mild photothermal therapy and significantly enhancing the efficacy of this therapy with encouraging synergistic anti-tumour effects. Overall, the integration of biochemical and optics strategies in this nanomotor platform represents a significant advancement in deep-tissue tumor therapy. It has substantial clinical translational value and is expected to have a transformative impact on future cancer treatments.

Evaluation of Antibacterial, Antibiofilm, Antioxidant, and Anti-Inflammatory Activities of Kratom Leaves (Mitragyna speciosa) Fermentation Supernatant Containing Lactobacillus rhamnosus GG

Kratom (Mitragyna speciosa) leaves are commonly used to enhance endurance and treat various diseases. This study evaluated the effect of kratom leaf fermentation with Lactobacillus rhamnosus. Antibacterial activity was investigated against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, and E. coli O157:H7. Biofilm inhibition and eradication assays were also performed. Antioxidant properties were determined by measuring the total phenolic and flavonoid content and DPPH and ABTS scavenging activities. Nitric oxide and TNF-α, IL-1β, and IL-6 expressions in LPS-stimulated RAW 264.7 macrophage cells were also measured. Aqueous kratom extract exhibited promising effects against free radicals and pro-inflammatory cytokines. Notably, all fermented kratoms showed significant antibacterial activity against the tested pathogens and antibiofilm formation by S. aureus and MRSA. Furthermore, the eradication of established biofilms of fermented kratoms was observed in S. aureus (day 2, 50 mg/mL) and E. coli (day 2, 100 mg/mL and day 4, 50 mg/mL). To the best of our knowledge, this study is the first to report that fermented and non-fermented kratoms could be nutraceutical sources of antibacterial, antibiofilm, antioxidant, and anti-inflammatory substances against related diseases and can be applied further in dietary or cosmetic products with health-promoting effects.

Prototype of Implant for Nitric Oxide Release Controlled by Infrared Radiation in Therapeutic Window

Local therapeutic action and targeted drug release are promising approaches compared to traditional systemic drug administration. This is especially relevant for nitric oxide (NO), as its effects change dramatically depending on concentration and cellular context. Materials capable of releasing NO in deep tissues in a controlled manner might open new therapeutic opportunities. Light-sensitive NO donors represent a fascinating class of compounds with significant potential for precise and controlled NO release. However, most of them are sensitive to visible light, with only a few examples absorbing in a near-infrared therapeutic window. Here, we present the proof-of-concept of soft implants consisting of the photon upconverting core and the outer shell loaded with visible-light triggered NO donor. The separation into two compartments results in efficient energy harvesting by the dye and effective NO release under 980 nm infrared irradiation. Such implants could be used in smart therapies implying well-controlled and localized NO release.

Chromium Complex of Macrocyclic Ligands as Precursor for Nitric Oxide Release: A Theoretical Study

Our research on the chromium complex of macrocyclic ligands as a precursor for nitric oxide release makes a significant contribution to the field of chemistry. We conduct a detailed analysis of nitrito chromium complexes, specifically trans-[M(III)L1-5(ONO)2]+, where M=Cr(III) and L1-L5 represent different ligands such as L1=1,4,8,11-tetraazacyclotetradecane, L2= (5,7-dimethyl-6-benzylcyclam), L3= (5,7-dimethyl-6-anthracylcyclam), L4= (5,7-dimethyl-6-(p-hydroxymethylbenzyl)-1,4, 8,11-cyclam) and L5= (5,7-dimethyl-6-(1¢-methyl-4'-(1"-carboxymethylpyrene) benzyl)-1,4,8,11-tetraazacyclotetradecane). Our objective is to comprehensively understand the mechanism of NO release and identify the key factors influencing NO delivery. The optimized structure of the complexes at spin states S=1/2 or 3/2 indicates a decrease in the Cr(III)-O bond length (1.669-1.671 Å) along with an increase in the Cr(III)O-NO bond length (2.735-2.741 Å), which facilitates the release of NO. Furthermore, there is a significant change in the bond angle (Cr-O-NO), from 120.4° to 116.9°, to S=3/2, thus enlarging the O-NO bond and supporting the β-cleavage of NO from the complex. The calculated activation energy for the complexes reflects the energy difference between the low-spin doublet and high-spin quartet state due to spin crossover (SCO). Moreover, the Natural Transition Orbitals (NTOs) confirm the involvement of a hole-particle in the excitation. Additionally, TD-DFT reveals the pendant chromophore's role in generating NO, as the chromophore antenna effectively enhances light absorption.

Bovine NMRAL2 Protein Blunts Nitric Oxide Production and Inflammatory Response in Mycobacterium bovis Infected Bovine Lung Epithelial Cells

Tuberculosis (TB), primarily caused by Mycobacterium tuberculosis (M. tb) and Mycobacterium bovis (M. bovis), remains the leading cause of death from a single infectious agent globally. Intracellular survival is crucial for their virulence; yet, the underlying mechanisms are not fully understood. This study aimed to demonstrate the significance of a previously unannotated bovine gene ENSBTAG00000011305 in M. bovis intracellular survival. This gene was termed NMRAL2_Bovine due to its inclusion of the NmrA domain which has a relation to nitric oxide (NO) production. We used CRISPR/Cas9 to knock out NMRAL2_Bovine in bovine lung epithelial cells and observed a significant decrease in M. bovis-induced cell death and the intracellular bacterial count, alongside increased NO levels. A transcriptome analysis revealed the upregulation of pathways linked to NO, IL-6, and TNF-α production, which was confirmed by the increased expression of iNOS, IL-6, and TNF-α. Correspondingly, Western blotting indicated that key signaling pathways, including NF-κB and MAPK, were activated. In conclusion, our findings determined that NMRAL2_Bovine functions as a negative regulator of the inflammatory response induced by M. bovis infection at the cellular level and, thereby, provide a novel insight into TB pathogenesis and a potential target for developing novel host-directed therapies against TB.

Biomimetic Activation of N-Nitrosamides with Red Light-Triggered Nitric Oxide Release via Mediated Electron Transfer

Mediated electron transfer (MET) is fundamental to many biological functions, including cellular respiration, photosynthesis, and enzymatic catalysis. However, leveraging the MET process to enable the release of therapeutic gases has been largely unexplored. Herein, we report the bio-inspired activation of a series of UV-absorbing N-nitrosamide derivatives (NOA) under red light exposure, enabling the quantitative release of nitric oxide (NO) gasotransmitter via an MET process. The cornerstone of our design is the covalent linkage of a 2,4-dinitroaniline moiety, which acts as an electron mediator to the N-nitrosamide groups. This facilitates efficient electron transfer from the excited palladium(II) meso-tetraphenyltetrabenzoporphyrin (PdTPTBP) photocatalyst and the selective activation of NOA. Our approach has been validated with distinct photocatalysts and various N-nitrosamides, including those derived from carbamates, amides, and ureas. Notably, the modulation of the linker length between the electron mediator and N-nitrosamide groups serves as a regulatory mechanism for controlling NO release kinetics. Moreover, this biomimetic NO release platform demonstrates effective operation under both normoxic and hypoxic conditions, and it enables localized delivery of NO under physiological conditions, exhibiting significant anticancer efficacy within the phototherapeutic window and enhanced selectivity towards tumor cells.

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.

Soursop leaf extract and fractions protects against L-NAME-induced hypertension and hyperlipidemia

Introduction

Despite the high phenolic content of Annona muricata, little is known about its anti-hypertensive and antihyperlipidemic properties. This study evaluated the anti-hypertensive and antihyperlipidemic potential of A. muricata leaf extracts.

Materials and methods

Forty-two male Wistar rats were divided into seven groups of six animals each. N-nitro-L-arginine methyl ester (L-NAME) was used to induce hypertension and hyperlipidemia.

Results

Phytochemical screening of Annona muricata leaf extracts (AMLE) revealed the presence of saponins, alkaloids, flavonoids, tannins, coumarins, steroids, terpenoids, and phenols. Comparing the methanol extract with the ethyl acetate fraction, quantification revealed that the methanol extract contained more phenolics, flavonoids, and alkaloids. The AMLE rats significantly reduced triglycerides, total cholesterol, LDL, VLDL, atherogenic index, coronary risk index, and blood pressure. The significant decrease in GSH, catalase, SOD, GST, and oxidative stress markers (MDA, nitrites, and MPO) was reversed by AMLE in a dose-dependent manner. Also, the elevated serum levels of TNF-α and IL-1β in the hypertensive rats were attenuated in the treatment groups.

Discussion

This study suggests the potential ameliorative effects of Annona muricata leaf extracts against L-NAME-induced hypertension in rats. Notably, the study showed the antioxidant and anti-inflammatory properties of A. muricata leaf extracts, which is seen in its ability to attenuate oxidative stress and inflammatory cytokines in L-NAME-induced hypertensive rats. A. muricata extracts also decreased atherogenic risk and improved lipid profiles.

Hydrogen Therapy Reverses Cancer-Associated Fibroblasts Phenotypes and Remodels Stromal Microenvironment to Stimulate Systematic Anti-Tumor Immunity

Tumor microenvironment (TME) plays an important role in the tumor progression. Among TME components, cancer-associated fibroblasts (CAFs) show multiple tumor-promoting effects and can induce tumor immune evasion and drug-resistance. Regulating CAFs can be a potential strategy to augment systemic anti-tumor immunity. Here, the study observes that hydrogen treatment can alleviate intracellular reactive oxygen species of CAFs and reshape CAFs' tumor-promoting and immune-suppressive phenotypes. Accordingly, a controllable and TME-responsive hydrogen therapy based on a CaCO3 nanoparticles-coated magnesium system (Mg-CaCO3) is developed. The hydrogen therapy by Mg-CaCO3 can not only directly kill tumor cells, but also inhibit pro-tumor and immune suppressive factors in CAFs, and thus augment immune activities of CD4+ T cells. As implanted in situ, Mg-CaCO3 can significantly suppress tumor growth, turn the "cold" primary tumor into "hot", and stimulate systematic anti-tumor immunity, which is confirmed by the bilateral tumor transplantation models of "cold tumor" (4T1 cells) and "hot tumor" (MC38 cells). This hydrogen therapy system reverses immune suppressive phenotypes of CAFs, thus providing a systematic anti-tumor immune stimulating strategy by remodeling tumor stromal microenvironment.

Fluorescent small molecule donors

Small molecule donors (SMDs) play subtle roles in the signaling mechanism and disease treatments. While many excellent SMDs have been developed, dosage control, targeted delivery, spatiotemporal feedback, as well as the efficiency evaluation of small molecules are still key challenges. Accordingly, fluorescent small molecule donors (FSMDs) have emerged to meet these challenges. FSMDs enable controllable release and non-invasive real-time monitoring, providing significant advantages for drug development and clinical diagnosis. Integration of FSMDs with chemotherapeutic, photodynamic or photothermal properties can take full advantage of each mode to enhance therapeutic efficacy. Given the remarkable properties and the thriving development of FSMDs, we believe a review is needed to summarize the design, triggering strategies and tracking mechanisms of FSMDs. With this review, we compiled FSMDs for most small molecules (nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, reactive oxygen species and formaldehyde), and discuss recent progress concerning their molecular design, structural classification, mechanisms of generation, triggered release, structure-activity relationships, and the fluorescence response mechanism. Firstly, from the large number of fluorescent small molecular donors available, we have organized the common structures for producing different types of small molecules, providing a general strategy for the development of FSMDs. Secondly, we have classified FSMDs in terms of the respective donor types and fluorophore structures. Thirdly, we discuss the mechanisms and factors associated with the controlled release of small molecules and the regulation of the fluorescence responses, from which universal guidelines for optical properties and structure rearrangement were established, mainly involving light-controlled, enzyme-activated, reactive oxygen species-triggered, biothiol-triggered, single-electron reduction, click chemistry, and other triggering mechanisms. Fourthly, representative applications of FSMDs for trackable release, and evaluation monitoring, as well as for visible in vivo treatment are outlined, to illustrate the potential of FSMDs in drug screening and precision medicine. Finally, we discuss the opportunities and remaining challenges for the development of FSMDs for practical and clinical applications, which we anticipate will stimulate the attention of researchers in the diverse fields of chemistry, pharmacology, chemical biology and clinical chemistry. With this review, we hope to impart new understanding thereby enabling the rapid development of the next generation of FSMDs.

Coumarin-Furoxan Hybrid Suppressed the Proliferation and Metastasis of Triple-Negative Breast Cancer by Activating Mitochondrial Stress and Cell Apoptosis

Triple-negative breast cancer (TNBC) typically manifests as higher invasive carcinoma correlated with a worse prognosis that primarily relies on chemotherapy. There is growing evidence that nitric oxide (NO) donor drugs have the potential for anticancer therapy. On this basis, we constructed and evaluated a novel coumarin-furoxan hybrid 4A93 as an effective antitumor candidate drug. 4A93 exhibits low IC50 values in three TNBC cell lines and inhibits colony formation and DNA synthesis, probably due to the release of high concentrations of NO in mitochondria, which induces oxidative stress, mitochondrial dysfunction, and apoptosis. Further research suggests that 4A93 might destroy mitochondria by opening the mitochondrial permeability transition pore (mPTP), depolarizing the mitochondrial membrane potential (MMP), and promoting the release of cytochrome c into the cytoplasm. Intrinsic apoptosis is induced finally, along with Akt/Erk signaling suppression. Additionally, 4A93 underregulates the Epithelial-mesenchymal transition process to inhibit cell migration and invasion. In 4T1 subcutaneous and hematogenous models of mice, 4A93 therapy suppresses the tumor growth and prevented lung metastasis with favorable biosafety. Our results provide insights into 4A93 in TNBC treatment and validate the contribution of NO donors in tumor therapy.

A NIR-II Photoacoustic Probe for High Spatial Quantitative Imaging of Tumor Nitric Oxide in Vivo

Nitric oxide (NO) exhibits both pro- and anti-tumor effects. Therefore, real-time in vivo imaging and quantification of tumor NO dynamics are essential for understanding the conflicting roles of NO played in pathophysiology. The current molecular probes, however, cannot provide high-resolution imaging in deep tissues, making them unsuitable for these purposes. Herein, we designed a photoacoustic probe with an absorption maximum beyond 1000 nm for high spatial quantitative imaging of in vivo tumor NO dynamics. The probe exhibits remarkable sensitivity, selective ratiometric response behavior, and good tumor-targeting abilities, facilitating ratiometric imaging of tumor NO throughout tumor progression in a micron-resolution level. Using the probe as the imaging agent, we successfully quantified NO dynamics in tumor, liver and kidney. We have pinpointed an essential concentration threshold of around 80 nmol/cm3 for NO, which plays a crucial role in the "double-edged-sword" function of NO in tumors. Furthermore, we revealed a reciprocal relationship between the NO concentration in tumors and that in the liver, providing initial insights into the possible NO-mediated communication between tumor and the liver. We believe that the probe will help resolve conflicting aspects of NO biology and guide the design of imaging agents for tumor diagnosis and anti-cancer drug screening.

Electronic Structure and Transformation of Dinitrosyl Iron Complexes (DNICs) Regulated by Redox Non-Innocent Imino-Substituted Phenoxide Ligand

The coupled NO-vibrational peaks [IR νNO 1775 s, 1716 vs, 1668 vs cm-1 (THF)] between two adjacent [Fe(NO)2] groups implicate the electron delocalization nature of the singly O-phenoxide-bridged dinuclear dinitrosyliron complex (DNIC) [Fe(NO)2(μ-ON2Me)Fe(NO)2] (1). Electronic interplay between [Fe(NO)2] units and [ON2Me]- ligand in DNIC 1 rationalizes that "hard" O-phenoxide moiety polarizes iron center(s) of [Fe(NO)2] unit(s) to enforce a "constrained" π-conjugation system acting as an electron reservoir to bestow the spin-frustrated {Fe(NO)2}9-{Fe(NO)2}9-[·ON2Me]2- electron configuration (Stotal = 1/2). This system plays a crucial role in facilitating the ligand-based redox interconversion, working in harmony to control the storage and redox-triggered transport of the [Fe(NO)2]10 unit, while preserving the {Fe(NO)2}9 core in DNICs {Fe(NO)2}9-[·ON2Me]2- [K-18-crown-6-ether)][(ON2Me)Fe(NO)2] (2) and {Fe(NO)2}9-[·ON2Me] [(ON2Me)Fe(NO)2][PF6] (3). Electrochemical studies suggest that the redox interconversion among [{Fe(NO)2}9-[·ON2Me]2-] DNIC 3 ↔ [{Fe(NO)2}9-[ON2Me]-] ↔ [{Fe(NO)2}9-[·ON2Me]] DNIC 2 are kinetically feasible, corroborated by the redox shuttle between O-bridged dimerized [(μ-ONMe)2Fe2(NO)4] (4) and [K-18-crown-6-ether)][(ONMe)Fe(NO)2] (5). In parallel with this finding, the electronic structures of [{Fe(NO)2}9-{Fe(NO)2}9-[·ON2Me]2-] DNIC 1, [{Fe(NO)2}9-[·ON2Me]2-] DNIC 2, [{Fe(NO)2}9-[·ON2Me]] DNIC 3, [{Fe(NO)2}9-[ONMe]-]2 DNIC 4, and [{Fe(NO)2}9-[·ONMe]2-] DNIC 5 are evidenced by EPR, SQUID, and Fe K-edge pre-edge analyses, respectively.

Effect of Electron-donating Group on NO Photolysis of {RuNO}6 Ruthenium Nitrosyl Complexes with N2 O2 Lgands Bearing π-Extended Rings

In this study, we introduced the electron-donating group (-OH) to the aromatic rings of Ru(salophen)(NO)Cl (0) (salophenH2 =N,N'-(1,2-phenylene)bis(salicylideneimine)) to investigate the influence of the substitution on NO photolysis and NO-releasing dynamics. Three derivative complexes, Ru((o-OH)2 -salophen)(NO)Cl (1), Ru((m-OH)2 -salophen)(NO)Cl (2), and Ru((p-OH)2 -salophen)(NO)Cl (3) were developed and their NO photolysis was monitored by using UV/Vis, EPR, NMR, and IR spectroscopies under white room light. Spectroscopic results indicated that the complexes were diamagnetic Ru(II)-NO+ species which were converted to low-spin Ru(III) species (d5 , S=1/2) and released NO radicals by photons. The conversion was also confirmed by determining the single-crystal structure of the photoproduct of 1. The photochemical quantum yields (ΦNO s) of the photolysis were determined to be 0>1, 2, 3 at both the visible and UV excitations. Femtosecond (fs) time-resolved mid-IR spectroscopy was employed for studying NO-releasing dynamics. The geminate rebinding (GR) rates of the photoreleased NO to the photolyzed complexes were estimated to be 0≃1, 2, 3. DFT and TDDFT computations found that the introduction of the hydroxyl groups elevated the ligand π-bonding orbitals (π (salophen)), resulting in decrease of the HOMO-LUMO gaps in 1-3. The theoretical calculations suggested that the Ru-NNO bond dissociations of the complexes were mostly initiated by the ligand-to-ligand charge transfer (LLCT) of π(salophen)→π*(Ru-NO) with both the visible and UV excitations and the decreasing ΦNO s could be explained by the changes of the electronic structures in which the photoactivable bands of 1-3 have relatively less contribution of transitions related with Ru-NO bond than those of 0.

A metabolic perspective on nitric oxide function in melanoma

Nitric oxide (NO) generated from nitric oxide synthase (NOS) exerts a dichotomous effect in melanoma, suppressing or promoting tumor progression. This dichotomy is thought to depend on the intracellular NO concentration and the cell type in which it is generated. Due to its central role in the metabolism of multiple critical constituents involved in signaling and stress, it is crucial to explore NO's contribution to the metabolic dysfunction of melanoma. This review will discuss many known metabolites linked to NO production in melanoma. We discuss the synthesis of these metabolites, their role in biochemical pathways, and how they alter the biological processes observed in the melanoma tumor microenvironment. The metabolic pathways altered by NO and the corresponding metabolites reinforce its dual role in melanoma and support investigating this effect for potential avenues of therapeutic intervention.

Controllable release of nitric oxide from an injectable alginate hydrogel

Currently, the controlled release of nitric oxide (NO) plays a crucial role in various biomedical applications. However, injectable NO-releasing materials remain an underexplored research field to date. In this study, via the incorporation of S-nitroso-N-acetyl-penicillamine (SNAP) as an NO donor, a family of NO-releasing injectable hydrogels was synthesized through the in situ cross-linking between sodium alginate and calcium ion induced by D-(+)-gluconate δ-lactone as an initiator. Initially, the organic functional groups and the corresponding morphologies of the resulting injectable hydrogels were characterized by IR and SEM spectroscopies, respectively. The NO release times of hydrogels with different SNAP loading amounts could reach up to 36-47 h. Due to the release of NO, the highest antibacterial rates of these injectable hydrogels against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were up to 95 %, respectively. Furthermore, the matrix of these hydrogels demonstrated great water absorption ability, swelling behavior, and degradation performance. Finally, we expect that these NO-releasing injectable hydrogels could have great potential applications various biomedical material fields.

Targeting CD24 in Cancer Immunotherapy

Immunotherapy is a hot area in cancer treatment, and one of the keys to this therapy is the identification of the right tumour-associated or tumour-specific antigen. Cluster of differentiation 24 (CD24) is an emerging tumour-associated antigen that is commonly and highly expressed in various tumours. In addition, CD24 is associated with several cancer-related signalling pathways and closely interacts with other molecules and immune cells to influence tumour progression. Monoclonal antibodies, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, and CAR-NK cell therapy are currently available for the treatment of CD24. In this review, we summarise the existing therapeutic approaches and possible future directions targeting CD24.

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.

Nitric oxide, thyroglobulin, and calcitonin: unraveling the nature of thyroid nodules

Background

Thyroid nodules (TN) are localized morphological changes in the thyroid gland and can be benign or malignant.

Objective

The present study investigates the relationships between biochemical markers in serum (s) and their homologs in washout (w) after fine-needle aspiration biopsy (FNAB) of the TN of interest and their correlation with cytology specimen findings.

Methods

We investigated the relationships between serum biochemical markers nitric oxide (NO), thyroglobulin (TG), and calcitonin (CT), their homologs in washout after FNAB of the TN of interest, and cytology findings of biopsy samples classified according to the Bethesda system for thyroid cytopathology in this study, which included 86 subjects.

Results

Washout TG (TGw) level positively correlates with the cytology finding of the biopsy. A higher level of TGw correlates with higher categories of the Bethesda classification and indicates a higher malignant potential. The levels of serum NO (NOs), serum TG (TGs), serum CT (CTs), and washout CT (CTw) do not correlate with the cytology finding of the biopsy, and the higher levels of washout NO (NOw) correspond to the more suspicious ultrasound findings.

Conclusion

The findings of our study suggest that TGw and NOw could be used as potential predictors of malignancy in TN.

Gas-assisted phototherapy for cancer treatment

Phototherapies, mainly including photodynamic and photothermal therapy, have made considerable strides in the field of cancer treatment. With the aid of phototherapeutic agents, reactive oxygen species (ROS) or heat are generated under light irradiation to selectively damage cancer cells. However, sole-modality phototherapy faces certain drawbacks, such as limited penetration of phototherapeutic agents into tumor tissues, inefficient ROS generation due to hypoxia, treatment-induced inflammation and resistance of tumor to treatment (e.g., high levels of antioxidants, expression of heat shock protein). Gas therapy, an emerging therapy approach that damages cancer cells by improving the level of certain gas at the tumor site, shows potential to overcome the challenges associated with phototherapies. In addition, with the rapid development of nanotechnology, gas-assisted phototherapy based on nanomedicines has emerged as a promising strategy to enhance the treatment efficacy. This review summarizes recent advances in gas-assisted phototherapy and discusses the prospects and challenges of this strategy in cancer phototherapy.

Understanding the Photodynamic Therapy Induced Bystander and Abscopal Effects: A Review

Photodynamic therapy (PDT) is a clinically approved minimally/non-invasive treatment modality that has been used to treat various conditions, including cancer. The bystander and abscopal effects are two well-documented significant reactions involved in imparting long-term systemic effects in the field of radiobiology. The PDT-induced generation of reactive oxygen and nitrogen species and immune responses is majorly involved in eliciting the bystander and abscopal effects. However, the results in this regard are unsatisfactory and unpredictable due to several poorly elucidated underlying mechanisms and other factors such as the type of cancer being treated, the irradiation dose applied, the treatment regimen employed, and many others. Therefore, in this review, we attempted to summarize the current knowledge regarding the non-targeted effects of PDT. The review is based on research published in the Web of Science, PubMed, Wiley Online Library, and Google Scholar databases up to June 2023. We have highlighted the current challenges and prospects in relation to obtaining clinically relevant robust, reproducible, and long-lasting antitumor effects, which may offer a clinically viable treatment against tumor recurrence and metastasis. The effectiveness of both targeted and untargeted PDT responses and their outcomes in clinics could be improved with more research in this area.

Gas and light: triggers of c-di-GMP-mediated regulation

The widespread bacterial second messenger c-di-GMP is responsible for regulating many important physiological functions such as biofilm formation, motility, cell differentiation, and virulence. The synthesis and degradation of c-di-GMP in bacterial cells depend, respectively, on diguanylate cyclases and c-di-GMP-specific phosphodiesterases. Since c-di-GMP metabolic enzymes (CMEs) are often fused to sensory domains, their activities are likely controlled by environmental signals, thereby altering cellular c-di-GMP levels and regulating bacterial adaptive behaviors. Previous studies on c-di-GMP-mediated regulation mainly focused on downstream signaling pathways, including the identification of CMEs, cellular c-di-GMP receptors, and c-di-GMP-regulated processes. The mechanisms of CME regulation by upstream signaling modules received less attention, resulting in a limited understanding of the c-di-GMP regulatory networks. We review here the diversity of sensory domains related to bacterial CME regulation. We specifically discuss those domains that are capable of sensing gaseous or light signals and the mechanisms they use for regulating cellular c-di-GMP levels. It is hoped that this review would help refine the complete c-di-GMP regulatory networks and improve our understanding of bacterial behaviors in changing environments. In practical terms, this may eventually provide a way to control c-di-GMP-mediated bacterial biofilm formation and pathogenesis in general.

S-Ethyl-Isothiocitrullin-Based Dipeptides and 1,2,4-Oxadiazole Pseudo-Dipeptides: Solid Phase Synthesis and Evaluation as NO Synthase Inhibitors

We previously reported dipeptidomimetic compounds as inhibitors of neuronal and/or inducible NO synthases (n/iNOS) with significant selectivity against endothelial NOS (eNOS). They were composed of an S-ethylisothiocitrullin-like moiety linked to an extension through a peptide bond or a 1,2,4-oxadiazole link. Here, we developed two further series where the extension size was increased to establish more favorable interactions in the NOS substrate access channel. The extension was introduced on the solid phase by the reductive alkylation of an amino-piperidine moiety or an aminoethyl segment in the case of dipeptide-like and 1,2,4-oxadiazole compounds, respectively, with various benzaldehydes. Compared to the previous series, more potent inhibitors were identified with IC₅₀ in the micromolar to the submicromolar range, with significant selectivity toward nNOS. As expected, most compounds did not inhibit eNOS, and molecular modeling was carried out to characterize the reasons for the selectivity toward nNOS over eNOS. Spectral studies showed that compounds were interacting at the heme active site. Finally, selected inhibitors were found to inhibit intra-cellular iNOS and nNOS expressed in RAW264.7 and INS-1 cells, respectively.

"Iridium Signature" Mass Spectrometric Probes: New Tools Integrated in a Liquid Chromatography-Mass Spectrometry Workflow for Routine Profiling of Nitric Oxide and Metabolic Fingerprints in Cells

Nitric oxide (NO) is a highly reactive signaling molecule involved in diverse biological processes. Simultaneous profiling of NO and associated metabolic fingerprints in a single assay allows more accurate assessments of cell states and offers the possibility to better understand its exact biological roles. Herein, a multiplexing LC-MS workflow was established for simultaneous detection of intracellular NO and various metabolites based on a novel "iridium signature" mass spectrometric probe (Ir-MSP841). This Ir-MSP841 can convert highly liable NO to a stable permanently charged triazole product (Ir-TP852), enabling direct MS detection of NO. This ^191/193Ir-signature mass spectrometric probe-based approach is endowed with overwhelming advantages of interference-free, high quantitative accuracy, and great sensitivity (limit of detection down to 0.14 nM). It also reveals good linearity over a wide concentration range 12.5-500 nM and has been successfully employed for exploring the release behaviors of three representative NO donors in cells. Meanwhile, metabolic profiling results reveal that varying the concentrations of NO has distinct effects on various cellular metabolites. This study provides a robust, sensitive, and versatile method for simultaneous detection of NO and numerous metabolites in a single LC-MS run and expands its applications in biomedical research.

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.

The Interplay between T Cells and Cancer: The Basis of Immunotherapy

Over the past decade, immunotherapy has emerged as one of the most promising approaches to cancer treatment. The use of immune checkpoint inhibitors has resulted in impressive and durable clinical responses in the treatment of various cancers. Additionally, immunotherapy utilizing chimeric antigen receptor (CAR)-engineered T cells has produced robust responses in blood cancers, and T cell receptor (TCR)-engineered T cells are showing promising results in the treatment of solid cancers. Despite these noteworthy advancements in cancer immunotherapy, numerous challenges remain. Some patient populations are unresponsive to immune checkpoint inhibitor therapy, and CAR T cell therapy has yet to show efficacy against solid cancers. In this review, we first discuss the significant role that T cells play in the body's defense against cancer. We then delve into the mechanisms behind the current challenges facing immunotherapy, starting with T cell exhaustion due to immune checkpoint upregulation and changes in the transcriptional and epigenetic landscapes of dysfunctional T cells. We then discuss cancer-cell-intrinsic characteristics, including molecular alterations in cancer cells and the immunosuppressive nature of the tumor microenvironment (TME), which collectively facilitate tumor cell proliferation, survival, metastasis, and immune evasion. Finally, we examine recent advancements in cancer immunotherapy, with a specific emphasis on T-cell-based treatments.

Interstitial Cells of Cajal and Enteric Nervous System in Gastrointestinal and Neurological Pathology, Relation to Oxidative Stress

The enteric nervous system (ENS) is organized into two plexuses-submucosal and myenteric-which regulate smooth muscle contraction, secretion, and blood flow along the gastrointestinal tract under the influence of the rest of the autonomic nervous system (ANS). Interstitial cells of Cajal (ICCs) are mainly located in the submucosa between the two muscle layers and at the intramuscular level. They communicate with neurons of the enteric nerve plexuses and smooth muscle fibers and generate slow waves that contribute to the control of gastrointestinal motility. They are also involved in enteric neurotransmission and exhibit mechanoreceptor activity. A close relationship appears to exist between oxidative stress and gastrointestinal diseases, in which ICCs can play a prominent role. Thus, gastrointestinal motility disorders in patients with neurological diseases may have a common ENS and central nervous system (CNS) nexus. In fact, the deleterious effects of free radicals could affect the fine interactions between ICCs and the ENS, as well as between the ENS and the CNS. In this review, we discuss possible disturbances in enteric neurotransmission and ICC function that may cause anomalous motility in the gut.

Thermosusceptible Nitric-Oxide-Releasing Nitrogel for Strengthening Antitumor Immune Responses with Tumor Collagen Diminution and Deep Tissue Delivery during NIR Laser-Assisted Photoimmunotherapy

Combined cancer immunotherapy has demonstrated promising potential with an amplified antitumor response and immunosuppressive tumor microenvironment (TME) modulation. However, one of the main issues that cause treatment failure is the poor diffusion and insufficient penetration of therapeutic and immunomodulatory agents in solid tumors. Herein, a cancer treatment approach that combines photothermal therapy (PTT) and nitric oxide (NO) gas therapy for tumor extracellular matrix (ECM) degradation, along with NLG919, an indoleamine 2,3-dioxygenase (IDO) inhibitor that reduces tryptophan catabolism to kynurenine, and DMXAA, a stimulator of interferon gene (STING) agonist that stimulates antigen cross-presentation, is proposed to overcome this issue. Upon NIR (808 nm) laser irradiation, NO-GEL achieved the desired thermal ablation by releasing sufficient tumor antigens through immunogenic cell death (ICD). NO delivery triggered local diffusion of excess NO gas for effectively degrading tumor collagen in the ECM, homogeneously delivered NLG919 throughout the tumor tissue, inhibited IDO expression that was upregulated by PTT, and reduced the immune suppressive activities. The sustained release of DMXAA prolonged dendritic cell maturation and CD8⁺ T cell activation against the tumor. In summary, NO-GEL therapeutics offer a significant tumor regression with PTT and STING agonist combination that stimulates a durable antitumor immune response. Additional unification of IDO inhibition during PTT supplements the immunotherapy by reducing the T cell apoptosis and immune suppressive cell infiltration to TME. NO-GEL with the STING agonist and IDO inhibitor is an effective therapeutic combination to counter possible limitations during solid tumor immunotherapy.

Newly developed gas-assisted sonodynamic therapy in cancer treatment

Sonodynamic therapy (SDT) is an emerging noninvasive treatment modality that utilizes low-frequency and low-intensity ultrasound (US) to trigger sensitizers to kill tumor cells with reactive oxygen species (ROS). Although SDT has attracted much attention for its properties including high tumor specificity and deep tissue penetration, its anticancer efficacy is still far from satisfactory. As a result, new strategies such as gas-assisted therapy have been proposed to further promote the effectiveness of SDT. In this review, the mechanisms of SDT and gas-assisted SDT are first summarized. Then, the applications of gas-assisted SDT for cancer therapy are introduced and categorized by gas types. Next, therapeutic systems for SDT that can realize real-time imaging are further presented. Finally, the challenges and perspectives of gas-assisted SDT for future clinical applications are discussed.

Hypoxia-Activatable Nanovesicles as In Situ Bombers for Combined Hydrogen-Sulfide-Mediated Respiration Inhibition and Photothermal Therapy

Photothermal therapy (PTT) has emerged as a promising alternative or supplement to cancer treatments. While PTT induces the ablation of solid tumors, its efficiency is hampered by self-recovery within impaired cancer cells through glycolysis and respiration metabolism. Based on this, the introduction of hydrogen sulfide (H₂S)-mediated respiration inhibition is a good choice to make up for the PTT limitation. Herein, nanovesicles (NP1) are integrated by a hypoxia-responsive conjugated polymer (P1), polymetric H₂S donor (P2), and near-infrared (NIR) light-harvesting aza-BODIPY dye (B1) for the delivery of H₂S and synergistic H₂S gas therapy/PTT. The scaffold of NP1 undergoes disassembly in the hypoxic environments, thus triggering the hydrolysis of P2 to continuously long-term release H₂S. Dependent on the superior photothermal ability of B1, NP1 elicits high photothermal conversion efficiency (η = 19.9%) under NIR light irradiation for PTT. Moreover, NP1 serves as in situ H₂S bombers in the hypoxic tumor environment and suppresses the mitochondrial respiration through inhibiting expression of cytochrome c oxidase (COX IV) and cutting off the adenosine triphosphate (ATP) generation. Both in vitro and in vivo results demonstrate good antitumor efficacy of H₂S gas therapy/PTT, which will be recommended as an advanced strategy for cancer therapeutics.

Effects of combination docetaxel with NO treatment to enhance the anti-nasopharyngeal carcinoma efficiency in vitro and in vivo

Nasopharyngeal carcinoma (NPC) is one of the major causes of death in Southern China. Due to the insidious location of NPC, the therapeutic effect of locoregionally advanced NPC is still unsatisfactory. In this work, to improve the treatment efficiency, combining DOC and JS-K to inhibit NPC cells (HNE-1) in vitro was investigated, as well as its possible mechanisms. Moreover, the in vivo effects of DOC and JS-K combination treatment were also evaluated in a xenograft model with HNE-1 cells. In vitro experiments including cell proliferation, migration ability, apoptosis, and expression levels of apoptosis-associated proteins revealed that the combination of DOC and JS-K was able to enhance antitumor effects. In vivo results further confirmed a significant treatment effect without obvious toxicity on mice. The present work provides a promising idea for the treatment of locally advanced NPC.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

Two-photon absorption-based delivery of nitric oxide from ruthenium nitrosyl complexes

Since the discovery of the numerous physiological roles exhibited by nitric oxide (NO), ruthenium nitrosyl (RuNO) complexes have been regarded as one of the most promising NO donors, stable, well tolerated by the body and capable of releasing NO locally and quantitatively, under light irradiation. This release can be achieved by two-photon absorption (TPA) processes, which allow the irradiation to be performed in the near infrared domain, where light has its maximum depth of penetration in biological tissues. This review provides a short introduction on the biological properties of NO, on RuNO complexes with photo-releasing capabilities, and on the origin of TPA properties in molecules. Then, the RuNO complexes with TPA capabilities are thoroughly discussed either as monometallic or polymetallic species.

Design, synthesis, and molecular docking of novel pyrazole-chalcone analogs of lonazolac as 5-LOX, iNOS and tubulin polymerization inhibitors with potential anticancer and anti-inflammatory activities

Uncontrolled inflammation predisposes to pleiotropic effects leading to cancer development thanks to promoting all stages of tumorigenesis. Therefore, cancer-associated inflammation has been delegated as the seventh hallmark of cancer. Thus, raging the war against both inflammation and cancer via the innovation of bioactive agents with dual anti-inflammatory and anticancer activities is a necessity. Herein, a novel series of pyrazole-chalcone analogs of Lonazolac (7a-g and 8a-g) have been synthesized and investigated for their in vitro anticancer activity against four cancer cell lines using the MTT assay method. Among all, hybrid 8g was the most potent against three cancer cell lines, HeLa, HCT-116, and RPMI-822 with IC₅₀ values of 2.41, 2.41, and 3.34 µM, respectively. In contrast, hybrid 8g showed moderate inhibitory activity against MCF-7 with IC₅₀ 28.93 μM and with a selectivity profile against MCF-10A (non-cancer cells). Mechanistically, hybrid 8g was the most potent inhibitor against tubulin polymerization (IC₅₀ = 4.77 µM), suggesting tubulin as a molecular target and explaining the observed cytotoxicity of hybrid 8g. This was mirrored by the detected potent pre-G1 apoptosis induction and G2/M cell cycle arrest. Moreover, hybrid8gexhibited selectivity against COX-2 (IC₅₀ = 5.13 µM) more than COX-1 (IC₅₀ = 33.46 µM), indicating that 8g may have lower cardiovascular side effects, but is still not potent as celecoxib (COX-2 IC₅₀ = 0.204 µM, COX-1 = 35.8 µM). Notably, hybrid 8g showed promising inhibitory activity towards 5-LOX (IC₅₀ = 5.88 µM). Finally, the anti-inflammatory activity of hybrid8 g was confirmed by high iNOS and PGE2 inhibitory activities in LPS-stimulated RAW cells with IC₅₀ values of4.93 µM and 10.98 µM, respectively, that accompanied by showingthe most potent inhibition of NO release (70.61 % inhibition rate). Molecular docking studies of hybrid 8g confirmed good correlations with the executed biological results. Furthermore, hybrid 8g had good drug-likeness and suitable physicochemical properties. Taken together, the combined results suggested hybrid8gas a promising orally administered candidate in the journey of repurposing NSAIDs for cancer chemopreventionand treatment.

Targeting amino acid metabolism in cancer

Metabolic rewiring is a characteristic hallmark of cancer cells. This phenomenon sustains uncontrolled proliferation and resistance to apoptosis by increasing nutrients and energy supply. However, reprogramming comes together with vulnerabilities that can be used against tumor and can be applied in targeted therapy. In the last years, the genetic background of tumors has been identified thoroughly and new therapies targeting those mutations tested. Nevertheless, we propose that targeting the phenotype of cancer cells could be another way of treatment aiming to avoid drug resistance and non-responsiveness of cancer patients. Amino acid metabolism is part of the altered processes in cancer cells. Amino acids are building blocks and also sensors of signaling pathways regulating main biological processes. In this comprehensive review, we described four amino acids (asparagine, arginine, methionine, and cysteine) which have been actively investigated as potential targets for anti-tumor therapy. Asparagine depletion is successfully used for decades in the treatment of acute lymphoblastic leukemia and there is a strong implication to apply it to other types of tumors. Arginine auxotrophic tumors are great candidates for arginine-starvation therapy. Higher requirement for essential amino acids such as methionine and cysteine point out promising targetable weaknesses of cancer cells.

Controllable Nitric Oxide Storage and Release in Cu-BTC: Crystallographic Insights and Bioactivity

Crystalline metal–organic frameworks (MOFs) are extensively used in areas such as gas storage and small-molecule drug delivery. Although Cu-BTC (1, MOF-199, BTC: benzene-1,3,5-tricarboxylate) has versatile applications, its NO storage and release characteristics are not amenable to therapeutic usage. In this work, micro-sized Cu-BTC was prepared solvothermally and then processed by ball-milling to prepare nano-sized Cu-BTC (2). The NO storage and release properties of the micro- and nano-sized Cu-BTC MOFs were morphology dependent. Control of the hydration degree and morphology of the NO delivery vehicle improved the NO release characteristics significantly. In particular, the nano-sized NO-loaded Cu-BTC (NO⊂nano-Cu-BTC, 4) released NO at 1.81 µmol·mg⁻¹ in 1.2 h in PBS, which meets the requirements for clinical usage. The solid-state structural formula of NO⊂Cu-BTC was successfully determined to be [CuC₆H₂O₅]·(NO)_0.167 through single-crystal X-ray diffraction, suggesting no structural changes in Cu-BTC upon the intercalation of 0.167 equivalents of NO within the pores of Cu-BTC after NO loading. The structure of Cu-BTC was also stably maintained after NO release. NO⊂Cu-BTC exhibited significant antibacterial activity against six bacterial strains, including Gram-negative and positive bacteria. NO⊂Cu-BTC could be utilized as a hybrid NO donor to explore the synergistic effects of the known antibacterial properties of Cu-BTC.

Visible-light NO photolysis of ruthenium nitrosyl complexes with N2O2 ligands bearing π-extended rings and their photorelease dynamics

NO photorelease and its dynamics for two {RuNO}⁶ complexes, Ru(salophen)(NO)Cl (1) and Ru(naphophen)(NO)Cl (2), with salen-type ligands bearing π-extended systems (salophenH₂ = N,N'-(1,2-phenylene)-bis(salicylideneimine) and naphophenH₂ = N,N'-1,2-phenylene-bis(2-hydroxy-1-naphthylmethyleneimine)) were investigated. NO photolysis was performed under white room light and monitored by UV/Vis, EPR, and NMR spectroscopies. NO photolysis was also performed under 459 and 489 nm irradiation for 1 and 2, respectively. The photochemical quantum yields of the NO photolysis (Φ_NO) of both 1 and 2 were determined to be 9% at the irradiation wavelengths. The structural and spectroscopic characteristics of the complexes before and after the photolysis confirmed the conversion of diamagnetic Ru(II)(L)(Cl)-NO⁺ to paramagnetic S = ½ Ru(III)(L)(Cl)-solvent by photons (L = salophen^2- and naphophen^2-). The photoreleased NO radicals were detected by spin-trapping EPR. DFT and TDDFT calculations found that the photoactive bands are configured as mostly the ligand-to-ligand charge transfer (LLCT) of π(L) → π*(Ru-NO), suggesting that the NO photorelease was initiated by the LLCT. Dynamics of NO photorelease from the complexes in DMSO under 320 nm excitation were investigated by femtosecond (fs) time-resolved mid-IR spectroscopy. The primary photorelease of NO occurred for less than 0.32 ps after the excitation. The rate constants (k_-1) of the geminate rebinding of NO to the photolyzed 1 and 2 were determined to be (15 ps)^-1 and (13 ps)^-1, respectively. The photochemical quantum yields of NO photolysis (Φ_NO, λ = 320 nm) were estimated to be no higher than 14% for 1 and 11% for 2, based on the analysis of the fs time-resolved IR data. The results of fs time-resolved IR spectroscopy and theoretical calculations provided some insight into the overall kinetic reaction pathway, localized electron pathway or resonance pathway, of the NO photolysis of 1 and 2. Overall, our study found that the investigated {RuNO}⁶ complexes, 1 and 2, with planar N₂O₂ ligands bearing π-extended rings effectively released NO under visible light.

Perfluorocarbon Nanodroplets for Dual Delivery with Ultrasound/GSH-Responsive Release of Model Drug and Passive Release of Nitric Oxide

Nitric oxide (NO) plays a critical role as an important signaling molecule for a variety of biological functions, particularly inhibiting cell proliferation or killing target pathogens. To deliver active radical NO gaseous molecule whose half-life is a few seconds in a stable state, the design and development of effective exogenous NO supply nanocarriers are essential. Additionally, the delivery of desired drugs with NO can produce synergistic effects. Herein, we report a new approach that allows for the fabrication of dual ultrasound (US)/glutathione (GSH)-responsive perfluorocarbon (PFC) nanodroplets for the controlled release of model drug and passive release of safely incorporated NO. The approach centers on the synthesis of a disulfide-labeled amphiphilic block copolymer and its use as a GSH-degradable macromolecular emulsifier for oil-in-water emulsification process of PFC. The fabricated PFC nanodroplets are colloidally stable and enable the encapsulation of both NO and model drugs. Encapsulated drug molecules are synergistically released when ultrasound and GSH are presented, while NO molecules are passively but rapidly released. Our preliminary results demonstrate that the approach is versatile and can be extended to not only GSH-responsive but also other stimuli-responsive block copolymers, thereby allowing for the fabrication of broad choices of stimuli-responsive (smart) PFC-nanodroplets in aqueous solution for dual delivery of drug and NO therapeutics.

Elevated ATG13 in serum of patients with ME/CFS stimulates oxidative stress response in microglial cells via activation of receptor for advanced glycation end products (RAGE)

Myalgic Encephalomyelitis, also known as Chronic Fatigue Syndrome (ME/CFS), is a multisystem illness characterized by extreme muscle fatigue associated with pain, neurocognitive impairment, and chronic inflammation. Despite intense investigation, the molecular mechanism of this disease is still unknown. Here we demonstrate that autophagy-related protein ATG13 is strongly upregulated in the serum of ME/CFS patients, indicative of impairment in the metabolic events of autophagy. A Thioflavin T-based protein aggregation assay, array screening for autophagy-related factors, densitometric analyses, and confirmation with ELISA revealed that the level of ATG13 was strongly elevated in serum samples of ME/CFS patients compared to age-matched controls. Moreover, our microglia-based oxidative stress response experiments indicated that serum samples of ME/CFS patients evoke the production of reactive oxygen species (ROS) and nitric oxide in human HMC3 microglial cells, whereas neutralization of ATG13 strongly diminishes the production of ROS and NO, suggesting that ATG13 plays a role in the observed stress response in microglial cells. Finally, an in vitro ligand binding assay provided evidence that ATG13 employs the Receptor for Advanced Glycation End-products (RAGE) to stimulate ROS in microglial cells. Collectively, our results suggest that an impairment of autophagy following the release of ATG13 into serum could be a pathological signal in ME/CFS.

Photosensitized co-generation of nitric oxide and singlet oxygen Enhanced toxicity against ovarian cancer cells

Near micromolar concentrations of nitric oxide (NO) induce tumor cells death. However, an appropriate NO load has to be delivered selectively to the tumor site in order to avoid NO loss and secondary NO-induced effects. The encapsulation of millimolar concentrations of a NO source and an appropriate trigger of NO release within phospatidylcholine-based liposomes should provide an efficient tool for the selective release of the needed NO payload. In this work we report the photosensitized generation of singlet oxygen and NO from folate-targeted PEGylated liposomes, containing AlPcS4 as the sensitizer and S-nitrosoglutathione (GSNO), in millimolar amounts, as the NO source. Amounts of singlet oxygen detected outside the liposome when using PEGylated liposomes are near 200 % larger when GSNO is present inside the liposomes as compared to its absence. These liposomes, conjugated to folate, were found to enhance the photosensitized cytotoxicity to A2780CP20 ovarian cancer cells as compared to liposomes containing the sensitizer but no GSNO (30 % as compared to 70 % cell viability) under the conditions of this work. Fluorescense of AlPcS4 was observed inside cells incubated with folate-conjugated liposomes but not with liposomes without folate. The photosensitized activity enhancement by GSNO increased when light fluence or liposome concentration were increased. The majority of ovarian cancer patients are initially diagnosed with disseminated intra-abdominal disease (stages III-IV) and have a 5-year survival of less than 20%. This work suggests a novel ovarian cancer nodules treatment via the use of tumor-targeted liposome nanoparticles with the capability of generating simultaneously reactive oxygen and nitrogen species upon illumination with near-infrared light.

Leveraging macrophages for cancer theranostics

As fundamental immune cells in innate and adaptive immunity, macrophages engage in a double-edged relationship with cancer. Dissecting the character of macrophages in cancer development facilitates the emergence of macrophages-based new strategies that encompass macrophages as theranostic targets/tools of interest for treating cancer. Herein, we provide a concise overview of the mixed roles of macrophages in cancer pathogenesis and invasion as a foundation for the review discussions. We survey the latest progress on macrophage-based cancer theranostic strategies, emphasizing two major strategies, including targeting the endogenous tumor-associated macrophages (TAMs) and engineering the adoptive macrophages to reverse the immunosuppressive environment and augment the cancer theranostic efficacy. We also discuss and provide insights on the major challenges along with exciting opportunities for the future of macrophage-based cancer theranostic approaches.

Strategies to improve the EPR effect: A mechanistic perspective and clinical translation

Many efforts have been made to achieve targeted delivery of anticancer drugs to enhance their efficacy and to reduce their adverse effects. These efforts include the development of nanomedicines as they can selectively penetrate through tumor blood vessels through the enhanced permeability and retention (EPR) effect. The EPR effect was first proposed by Maeda and co-workers in 1986, and since then various types of nanoparticles have been developed to take advantage of the phenomenon with regards to drug delivery. However, the EPR effect has been found to be highly variable and thus unreliable due to the complex tumor microenvironment. Various physical and pharmacological strategies have been explored to overcome this challenge. Here, we review key advances and emerging concepts of such EPR-enhancing strategies. Furthermore, we analyze 723 clinical trials of nanoparticles with EPR enhancers and discuss their clinical translation.

Ultrasound-Induced Destruction of Nitric Oxide-Loaded Microbubbles in the Treatment of Thrombus and Ischemia-Reperfusion Injury

Objectives: Early recanalization of large vessels in thromboembolism, such as myocardial infarction and ischemic stroke, is associated with improved clinical outcomes. Nitric oxide (NO), a biological gas signaling molecule, has been proven to protect against ischemia-reperfusion injury (IRI). However, the underlying mechanisms remain to be explored. This study investigated whether NO could mitigate IRI and the role of NO during acoustic cavitation. Methods: In vivo, thrombi in the iliac artery of rats were induced by 5% FeCl₃. NO-loaded microbubbles (NO-MBs) and ultrasound (US) were used to treat thrombi. B-mode and Doppler US and histological analyses were utilized to evaluate the thrombolysis effect in rats with thrombi. Immunohistochemistry, immunofluorescence, and western blotting were conducted to investigate the underlying mechanisms of NO during acoustic cavitation. In vitro, hypoxia was used to stimulate cells, and NO-MBs were employed to alleviate oxidative stress and apoptosis. Results: We developed NO-MBs that significantly improve the circulation time of NO in vivo, are visible, and effectively release therapeutic gas under US. US-targeted microbubble destruction (UTMD) and NO-loaded UTMD (NO + UTMD) caused a significant decrease in the thrombus area and an increase in the recanalization rates and blood flow velocities compared to the control and US groups. We discovered that UTMD induced NO generation through activation of endothelial NO synthase (eNOS) in vivo. More importantly, we also observed significantly increased NO content and eNOS expression in the NO + UTMD group compared to the UTMD group. NO + UTMD can mitigate oxidative stress and apoptosis in the hind limb muscle without influencing blood pressure or liver and kidney functions. In vitro, NO-MBs alleviated oxidative stress and apoptosis in cells pretreated with hypoxia. Conclusion: Based on these data, UTMD affects the vascular endothelium by activating eNOS, and NO exerts a protective effect against IRI.

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.

The emerging roles of nitric oxide in ferroptosis and pyroptosis of tumor cells

Tumor cells can develop resistance to cell death which is divided into necrosis and programmed cell death (PCD). PCD, including apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Ferroptosis and pyroptosis, two new forms of cell death, have gradually been of interest to researchers. Boosting ferroptosis and pyroptosis of tumor cells could be a potential cancer therapy. Nitric oxide (NO) is a ubiquitous, lipophilic, highly diffusible, free-radical signaling molecule that plays various roles in tumorigenesis. In addition, NO also has regulatory mechanisms through S-nitrosylation that do not depend on the classic NO/sGC/cGMP signaling. The current tumor treatment strategy for NO is to promote cell death through promoting S-nitrosylation-induced apoptosis while multiple drawbacks dampen this tumor therapy. However, numerous studies have suggested that suppression of NO is perceived to active ferroptosis and pyroptosis, which could be a better anti-tumor treatment. In this review, ferroptosis and pyroptosis are described in detail. We summarize that NO influences ferroptosis and pyroptosis and infer that S-nitrosylation mediates ferroptosis- and pyroptosis-related signaling pathways. It could be a potential cancer therapy different from NO-induced apoptosis of tumor cells. Finally, the information shows the drugs that manipulate endogenous production and exogenous delivery of NO to modulate the levels of S-nitrosylation.

Cross-linking of S-nitrosothiolated AIEgens inside cancer cells to monitor NO release and reverse chemo-resistance

Nitric oxide (NO)-releasing platforms have been demonstrated as promising approaches for the reversal of multidrug resistance (MDR) in cancer cells due to the suppression of P-glycoprotein (P-gp). However, the non-specific systemic release of NO and difficulty in estimating the precise NO amount in target sites hindered their translational applications. Traditional bioimaging techniques which are responsive to NO molecules cannot distinguish between exogenous and endogenous NO. Herein we introduce S-nitrosothiol-functionalized tetraphenylethene (TPE-RSNO) to specifically monitor exogenous NO release and synergistically reverse MDR. TPE-RSNO can specifically respond to NO release and visualize NO delivery with fluorescence in living cells. Moreover, the elevated reactive oxygen species (ROS) in cancer cells triggered rapid NO release to reduce P-gp and thus synergistically increase the therapeutic effect of doxorubicin (DOX).

Macrophage Reprogramming and Cancer Therapeutics: Role of iNOS-Derived NO

Nitric oxide and its production by iNOS is an established mechanism critical to tumor promotion or suppression. Macrophages have important roles in immunity, development, and progression of cancer and have a controversial role in pro- and antitumoral effects. The tumor microenvironment consists of tumor-associated macrophages (TAM), among other cell types that influence the fate of the growing tumor. Depending on the microenvironment and various cues, macrophages polarize into a continuum represented by the M1-like pro-inflammatory phenotype or the anti-inflammatory M2-like phenotype; these two are predominant, while there are subsets and intermediates. Manipulating their plasticity through programming or reprogramming of M2-like to M1-like phenotypes presents the opportunity to maximize tumoricidal defenses. The dual role of iNOS-derived NO also influences TAM activity by repolarization to tumoricidal M1-type phenotype. Regulatory pathways and immunomodulation achieve this through miRNA that may inhibit the immunosuppressive tumor microenvironment. This review summarizes the classical physiology of macrophages and polarization, iNOS activities, and evidence towards TAM reprogramming with current information in glioblastoma and melanoma models, and the immunomodulatory and therapeutic options using iNOS or NO-dependent strategies.