A novel mitochondria-targeting tetrapeptide for subcellular delivery of nanoparticles

A two-photon iridium(III) complex probe for sensitive detection of SO2 derivatives in living cell mitochondria

The derivatives of sulfur dioxide (HSO₃^-) formed in the biological environment play a vital role in the circulation system. Excessive SO₂ derivatives will cause serious damage to the living system. Herein, a two-photon phosphorescent probe based on Ir(III) complex (named as Ir-CN) was designed and synthesized. Ir-CN is extremely selective and sensitive to SO₂ derivatives with significant phosphorescent enhancement and increased phosphorescent lifetime. The detection limit of Ir-CN for SO₂ derivatives reaches 0.17 μM. More importantly, Ir-CN preferentially accumulates in mitochondria, so bisulfite derivatives can be detected at subcellular level, which enriching the application of metal complex probe in biological detection. In addition, both single-photon and two-photon images can clearly show that Ir-CN is targeted to mitochondria. Benefits from its good biocompatibility, Ir-CN may be used as a reliable tool to detect SO₂ derivatives in mitochondrion of living cells.

A new triphenylphosphonium-conjugated amphipathic cationic peptide with improved cell-penetrating and ROS-targeting properties

We study for the first time whether triphenylphosphonium (TPP) moiety can improve cellular delivery and redox properties of amphipathic cationic peptides based on YRFK/YrFK cell-penetrating and cytoprotective motif. TPP moiety was found to increase reducing activity of both stereoisomeric peptides in solution and on electrode surface in association with TPP-mediated intramolecular interactions. Among TPP-conjugated peptides, newly synthesized TPP3-YrFK featured both increased antioxidant efficacy and proteolytic resistance. TPP-conjugated peptides preferably mitigated endogenic ROS in mitochondria and cytoplasm of model glioblastoma cells with increased oxidative status. This anti-ROS effect was accompanied by mild reversible decrease of reduced glutathione level in the cells with relatively weak change in glutathione redox forms ratio. Such low interference with cell redox status is in accordance with non-cytotoxic nature of the compounds. Intracellular concentrations of label-free peptides were analyzed by LC-MS/MS, which showed substantial TPP-promoted penetration of YrFK motif across cell plasma membrane. However, according to ΔΨ_m analysis, TPP moiety did not profoundly enhance peptide interaction with mitochondrial inner membrane. Our study clarifies the role of TPP moiety in cellular delivery of amphipathic cationic oligopeptides. The results suggest TPP moiety as a multi-functional modifier for the oligopeptides which is capable of improving cellular pharmacokinetics and antioxidant activity as well as targeting increased ROS levels. The results encourage further investigation of TPP3-YrFK as a peptide antioxidant with multiple benefits.

Subcellular delivery of lipid nanoparticles to endoplasmic reticulum and mitochondria

Primarily responsible for the biogenesis and metabolism of biomolecules, endoplasmic reticulum (ER) and mitochondria are gradually becoming the targets of therapeutic modulation, whose physiological activities and pathological manifestations determine the functional capacity and even the survival of cells. Drug delivery systems with specific physicochemical properties (passive targeting), or modified by small molecular compounds, polypeptides, and biomembranes demonstrating tropism for ER and mitochondria (active targeting) are able to reduce the nonselective accumulation of drugs, enhancing efficacy while reducing side effects. Lipid nanoparticles feature high biocompatibility, diverse cargo loading, and flexible structure modification, which are frequently used for subcellular organelle-targeted delivery of therapeutics. However, there is still a lack of systematic understanding of lipid nanoparticle-based ER and mitochondria targeting. Herein, we review the pathological significance of drug selectively delivered to the ER and mitochondria. We also summarize the molecular basis and application prospects of lipid nanoparticle-based ER and mitochondria targeting strategies, which may provide guidance for the prevention and treatment of associated diseases and disorders. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Restoration of Sarco/Endoplasmic Reticulum Ca2+-ATPase Activity Functions as a Pivotal Therapeutic Target of Anti-Glutamate-Induced Excitotoxicity to Attenuate Endoplasmic Reticulum Ca2+ Depletion

Glutamate-induced excitotoxicity is a pathological basis of many acute/chronic neurodegenerative diseases. Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2b) is a membrane-embedded P-type ATPase pump that manages the translocation of calcium ions (Ca²⁺) from cytosol into the lumen of the endoplasmic reticulum (ER) calcium stores. It participates in a wide range of biological functions in the central nervous system (CNS). However, the role of SERCA2b in glutamate-induced excitotoxicity and its mechanism must be elucidated. Herein, we demonstrate that SERCA2b mutants exacerbate the excitotoxicity of hypo-glutamate stimulation on HT22 cells. In this study, SERCA2b mutants accelerated Ca²⁺ depletion through loss-of-function (reduced pumping capacity) or gain-of-function (acquired leakage), resulting in ER stress. In addition, the occurrence of ER Ca²⁺ depletion increased mitochondria-associated membrane formation, which led to mitochondrial Ca²⁺ overload and dysfunction. Moreover, the enhancement of SERCA2b pumping capacity or inhibition of Ca²⁺ leakage attenuated Ca²⁺ depletion and impeded excitotoxicity in response to hypo-glutamate stimulation. In conclusion, SERCA2b mutants exacerbate ER Ca²⁺-depletion-mediated excitotoxicity in glutamate-sensitive HT22 cells. The mechanism of disruption is mainly related to the heterogeneity of SERCA2b mutation sites. Stabilization of SRECA2b function is a critical therapeutic approach against glutamate-induced excitotoxicity. These data will expand understanding of organelle regulatory networks and facilitate the discovery and creation of drugs against excitatory/inhibitory imbalance in the CNS.

Localization of Organelle Proteins by Isotope Tagging: Current status and potential applications in drug discovery research

Spatial proteomics has provided important insights into the relationship between protein function and subcellular location. Localization of Organelle Proteins by Isotope Tagging (LOPIT) and its variants are proteome-wide techniques, not matched in scale by microscopy-based or proximity tagging-based techniques, allowing holistic mapping of protein subcellular location and re-localization events downstream of cellular perturbations. LOPIT can be a powerful and versatile tool in drug discovery for unlocking important information on disease pathophysiology, drug mechanism of action, and off-target toxicity screenings. Here, we discuss technical concepts of LOPIT with its potential applications in drug discovery and development research.

Synergetic delivery of triptolide and Ce6 with light-activatable liposomes for efficient hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) has been known as the second common leading cancer worldwide, as it responds poorly to both chemotherapy and medication. Triptolide (TP), a diterpenoid triepoxide, is a promising treatment agent for its effective anticancer effect on multiple cancers including HCC. However, its clinical application has been limited owing to its severe systemic toxicities, low solubility, and fast elimination in the body. Therefore, to overcome the above obstacles, photo-activatable liposomes (LP) integrated with both photosensitizer Ce6 and chemotherapeutic drug TP (TP/Ce6-LP) was designed in the pursuit of controlled drug release and synergetic photodynamic therapy in HCC therapy. The TP encapsulated in liposomes accumulated to the tumor site due to the enhanced permeability and retention (EPR) effect. Under laser irradiation, the photosensitizer Ce6 generated reactive oxygen species (ROS) and further oxidized the unsaturated phospholipids. In this way, the liposomes were destroyed to release TP. TP/Ce6-LP with NIR laser irradiation (TP/Ce6-LP+L) showed the best anti-tumor effect both in vitro and in vivo on a patient derived tumor xenograft of HCC (PDXHCC). TP/Ce6-LP significantly reduced the side effects of TP. Furthermore, TP/Ce6-LP+L induced apoptosis through a caspase-3/PARP signaling pathway. Overall, TP/Ce6-LP+L is a novel potential treatment option in halting HCC progression with attenuated toxicity.

Silibinin-Albumin Nanoparticles: Characterization and Biological Evaluation Against Oxidative Stress-Stimulated Neurotoxicity Associated with Alzheimer's Disease

Alzheimer's disease (AD) is strongly associated with oxidative stress which can damage neural cells. Silibinin has shown potential antioxidative effects. However, due to its low solubility in water, silibinin provides low biological activity and bioavailability. Therefore, to increase its pharmacological effects, silibilin was encapsulated into human serum albumin (HSA) nanoparticles and well-characterized by DLS and TEM techniques. The antioxidant activity of silibinin-HSA nanoparticles was evaluated on LPS-induced oxidative stress in neuron-like cells (SH-SY5Y) through MTT, antioxidant activity and apoptotic assay. It was shown that the mean diameter of HSA and silibinin-HSA nanoparticles were 88 and 105 nm, respectively with a drug loading of 24.08%, drug encapsulation rate of 94.72%, and the yield of silibinin-HSA nanoparticles of around 83.41% and the HSA nano-formulation released silibinin for 15 h. The results displayed that cell viability was reduced by LPS (10 μg/mL), who's also determined to stimulate oxidative stress and apoptosis. However, co-incubation of cells with silibinin (50 μg/mL) or silibinin-HSA nanoparticles led to the recovery of cell viability, activation of SOD and CAT, increase of GSH content, and reduction of ROS level, Caspase-3 activity and fragmentation of DNA. It was also indicated that the neuroprotective and antioxidant activities of silibinin-HAS nanoparticles was greater than free silibinin, indicating that using albumin can be a potential formulation approach for improving the antioxidant efficacy of silibinin.

Quercetin Nanoparticle Ameliorates Lipopolysaccharide-Triggered Renal Inflammatory Impairment by Regulation of Sirt1/NF-KB Pathway

As a conventional complication of sepsis, acute kidney injury (AKI) is characterized by high incidence and mortality. Effective management methods are still lacking. Quercetin belongs to a kind of flavonoids that exerts many functions, for example anti-inflammation and anti-fibrosis. However, its function in sepsis AKI is uncertain. Our study therefore set out to assess the function of quercetin in AKI mice model induced by lipopolysaccharide (LPS) and human proximal tubular cells (HK-2), including the potential mechanisms. Quercetin was loaded onto a biodegradable polymer carrier (nanoparticle) to enhance its bioavailability. The data showed that quercetin administration strikingly improved renal dysfunction and ameliorated tubular injury caused by LPS in mice. In mice model and in cultured cells, quercetin pretreatment obviously restrained LPS-triggered cell apoptosis and inflammation, including generation of various cytokines. Moreover, the results from mice model and cell model showed that quercetin could diminish IκBα and p65 phosphorylation after LPS treatment. The most significant observation of this study was that quercetin elevated the expression of Sirt1. Transfection of Sirt1 specific shRNA mitigated the suppression of quercetin on cell apoptosis, inflammation and of NF-κB activation triggered by LPS. Therefore, these sequels indicate that quercetin protects against sepsis-associated AKI by upregulation Sirt1 expression through quenching NF-κB activation and may be an encouraging therapeutic agent for patients with sepsis-associated AKI.

Nanomedicines for Subcellular Targeting: The Mitochondrial Perspective

BACKGROUND

Over the past decade, there has been a surge in the number of mitochondrialactive therapeutics for conditions ranging from cancer to aging. Subcellular targeting interventions can modulate adverse intracellular processes unique to the compartments within the cell. However, there is a dearth of reviews focusing on mitochondrial nano-delivery, and this review seeks to fill this gap with regards to nanotherapeutics of the mitochondria.

METHODS

Besides its potential for a higher therapeutic index than targeting at the tissue and cell levels, subcellular targeting takes into account the limitations of systemic drug administration and significantly improves pharmacokinetics. Hence, an extensive literature review was undertaken and salient information was compiled in this review.

RESULTS

From literature, it was evident that nanoparticles with their tunable physicochemical properties have shown potential for efficient therapeutic delivery, with several nanomedicines already approved by the FDA and others in clinical trials. However, strategies for the development of nanomedicines for subcellular targeting are still emerging, with an increased understanding of dysfunctional molecular processes advancing the development of treatment modules. For optimal delivery, the design of an ideal carrier for subcellular delivery must consider the features of the diseased microenvironment. The functional and structural features of the mitochondria in the diseased state are highlighted and potential nano-delivery interventions for treatment and diagnosis are discussed.

CONCLUSION

This review provides an insight into recent advances in subcellular targeting, with a focus on en route barriers to subcellular targeting. The impact of mitochondrial dysfunction in the aetiology of certain diseases is highlighted, and potential therapeutic sites are identified.

Membrane Trafficking and Subcellular Drug Targeting Pathways

The movement of micro and macro molecules into and within a cell significantly governs several of their pharmacokinetic and pharmacodynamic parameters, thus regulating the cellular response to exogenous and endogenous stimuli. Trafficking of various pharmacological agents and other bioactive molecules throughout and within the cell is necessary for the fidelity of the cells but has been poorly investigated. Novel strategies against cancer and microbial infections need a deeper understanding of membrane as well as subcellular trafficking pathways and essentially regulate several aspects of the initiation and spread of anti-microbial and anti-cancer drug resistance. Furthermore, in order to avail the maximum possible bioavailability and therapeutic efficacy and to restrict the unwanted toxicity of pharmacological bioactives, these sometimes need to be functionalized with targeting ligands to regulate the subcellular trafficking and to enhance the localization. In the recent past the scenario drug targeting has primarily focused on targeting tissue components and cell vicinities, however, it is the membranous and subcellular trafficking system that directs the molecules to plausible locations. The effectiveness of the delivery platforms largely depends on their physicochemical nature, intracellular barriers, and biodistribution of the drugs, pharmacokinetics and pharmacodynamic paradigms. Most subcellular organelles possess some peculiar characteristics by which membranous and subcellular targeting can be manipulated, such as negative transmembrane potential in mitochondria, intraluminal delta pH in a lysosome, and many others. Many specialized methods, which positively promote the subcellular targeting and restrict the off-targeting of the bioactive molecules, exist. Recent advancements in designing the carrier molecules enable the handling of membrane trafficking to facilitate the delivery of active compounds to subcellular localizations. This review aims to cover membrane trafficking pathways which promote the delivery of the active molecule in to the subcellular locations, the associated pathways of the subcellular drug delivery system, and the role of the carrier system in drug delivery techniques.

Hypoxia-activated nanomedicines for effective cancer therapy

Hypoxia, a common characteristic in solid tumors, is found in phenotypically aggressive cancers that display resistance to typical cancer interventions. Due to its important role in tumor progression, tumor hypoxia has been considered as a primary target for cancer diagnosis and treatment. An advantage of hypoxia-activated nanomedicines is that they are inactive in normoxic cells. In hypoxic tumor tissues and cells, these nanomedicines undergo reduction by activated enzymes (usually through 1 or 2 electron oxidoreductases) to produce cytotoxic substances. In this review, we will focus on approaches to design nanomedicines that take advantage of tumor hypoxia. These approaches include: i) inhibitors of hypoxia-associated signaling pathways; ii) prodrugs activated by hypoxia; iii) nanocarriers responsive to hypoxia, and iv) bacteria mediated hypoxia targeting therapy. These strategies have guided and will continue to guide nanoparticle design in the near future. These strategies have the potential to overcome tumor heterogeneity to improve the efficiency of radiotherapy, chemotherapy and diagnosis.