Hydrogen sulfide decreases photodynamic therapy outcome through the modulation of the cellular redox state

Novel AP39-Loaded Liposomes Sustain the Release of Hydrogen Sulphide, Enhance Blood-Brain Barrier Permeation, and Abrogate Oxidative Stress-Induced Mitochondrial Dysfunction in Brain Cells

Background

Neurodegenerative diseases are often linked to oxidative stress (OS), which worsen neuroinflammation and cause neuronal damage. Managing OS with gasotransmitters such as hydrogen sulphide (H2S) is a promising therapeutic approach to protecting brain cells from oxidative damage. AP39, a mitochondria-targeted H2S donor, has shown neuroprotective potential by reducing OS and improving mitochondrial function. However, its clinical application is limited due to poor stability and rapid release, necessitating a drug delivery system to enhance therapeutic efficacy.

Purpose

This study aimed to develop a novel AP39-loaded liposomal formulation to provide controlled H2S release, facilitate AP39 permeation across the blood-brain barrier (BBB), and assess functional effects in mitigating oxidative stress and preserving mitochondrial function.

Methods

AP39-loaded unilamellar liposomes were prepared via ethanol injection and characterised for size, polydispersity, and zeta potential. Entrapment efficiency was determined using HPLC, while cytotoxicity was assessed in human vein endothelial (HUVEC) and neuroblastoma (SHSY5Y) cells. Liposomal permeability, AP39 release kinetics, and cellular uptake were evaluated using a microvasculature BBB model. Mitochondrial function under oxidative stress was assessed using a Seahorse XFe24 Analyzer.

Results

AP39-loaded liposomes had an average size of 135.92 ± 10.05 nm, a zeta potential of 17.35 ± 3.40 mV, and an entrapment efficiency of 84.48% ± 4.7. Cytotoxicity studies showed no adverse effects after 4 h. Cellular uptake of encapsulated AP39 was significantly higher (7.13 ± 0.28 µg) than the free form (5.8 ± 0.31 µg). The BBB model demonstrated sustained AP39 release (7.28 µg/mL vs 6.44 µg/mL for free AP39). Mitochondrial assays confirmed liposomal AP39 preserved H2S antioxidant properties and enhanced oxygen consumption.

Conclusion

Our novel liposomal formulation encapsulating AP39 improves stability, promotes sustained release, and enhances BBB permeability while preserving antioxidant effects. These findings indicate that liposomal AP39 is a suitable therapeutic approach to further investigate in the treatment of neurodegenerative diseases.

NO- and H2S- releasing nanomaterials: A crosstalk signaling pathway in cancer

The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) play important roles not only in maintaining physiological functions, but also in pathological conditions and events. Importantly, these molecules show a complex interplay in cancer biology, demonstrating both tumor-promoting and anti-tumor activities depending on their concentration, flux, and the environmental redox state. Additionally, various cell types respond differently to NO and H2S. These gasotransmitters can be synergistically combined with traditional anticancer treatments such as radiotherapy, immunotherapy, chemotherapy, and phototherapy. Notably, NO, and more recently H2S, have been shown to reverse multidrug resistance. Nanomaterials to deliver NO donors and, to a lesser extent, H2S donors, have emerged as a promising approach for targeted delivery of these gasotransmitters. Nanotechnology has advanced the delivery of anticancer drugs, enhancing efficiency and reducing side effects on non-cancerous cells. This review highlights recent progress in the design of NO and H2S-releasing nanomaterials for anticancer effects. It also explores the interactions between NO and H2S, which are crucial for developing combined therapies and nanomedicines with minimal side effects.

Current trends in gas-synergized phototherapy for improved antitumor theranostics

Phototherapy, such as photothermal therapy (PTT) and photodynamic therapy (PDT), has been considered an elegant solution to eradicate tumors due to its minimal invasiveness and low systemic toxicity. Nevertheless, it is still challenging for phototherapy to achieve ideal outcomes and clinical translation due to its inherent drawbacks. Owing to the unique biological functions, diverse gases have attracted growing attention in combining with phototherapy to achieve super-additive therapeutic effects. Specifically, gases such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) have been proven to kill tumor cells by inducing mitochondrial damage in synergy with phototherapy. Additionally, several gases not only enhance the thermal damage in PTT and the reactive oxygen species (ROS) production in PDT but also improve the tumor accumulation of photoactive agents. The inflammatory responses triggered by hyperthermia in PTT are also suppressed by the combination of gases. Herein, we comprehensively review the latest studies on gas-synergized phototherapy for cancer therapy, including (1) synergistic mechanisms of combining gases with phototherapy; (2) design of nanoplatforms for gas-synergized phototherapy; (3) multimodal therapy based on gas-synergized phototherapy; (4) imaging-guided gas-synergized phototherapy. Finally, the current challenges and future opportunities of gas-synergized phototherapy for tumor treatment are discussed. STATEMENT OF SIGNIFICANCE: 1. The novelty and significance of the work with respect to the existing literature. (1) Strategies to design nanoplatforms for gas-synergized anti-tumor phototherapy have been summarized for the first time. Meanwhile, the integration of various imaging technologies and therapy modalities which endow these nanoplatforms with advanced theranostic capabilities has been summarized. (2) The mechanisms by which gases synergize with phototherapy to eradicate tumors are innovatively and comprehensively summarized. 2. The scientific impact and interest. This review elaborates current trends in gas-synergized anti-tumor phototherapy, with special emphases on synergistic anti-tumor mechanisms and rational design of therapeutic nanoplatforms to achieve this synergistic therapy. It aims to provide valuable guidance for researchers in this field.