Delivery of drugs and macromolecules to mitochondria

A Systematic Review of Carotenoids in the Management of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) remains a leading cause of modifiable vision loss in older adults. Chronic oxidative injury and compromised antioxidant defenses represent essential drivers in the development of retinal neurodegeneration. Overwhelming free radical species formation results in mitochondrial dysfunction, as well as cellular and metabolic imbalance, which becomes exacerbated with increasing age. Thus, the depletion of systemic antioxidant capacity further proliferates oxidative stress in AMD-affected eyes, resulting in loss of photoreceptors, neuroinflammation, and ultimately atrophy within the retinal tissue. The aim of this systematic review is to examine the neuroprotective potential of the xanthophyll carotenoids lutein, zeaxanthin, and meso-zeaxanthin on retinal neurodegeneration for the purpose of adjunctive nutraceutical strategy in the management of AMD. A comprehensive literature review was performed to retrieve 55 eligible publications, using four database searches from PubMed, Embase, Cochrane Library, and the Web of Science. Epidemiology studies indicated an enhanced risk reduction against late AMD with greater dietary consumption of carotenoids, meanwhile greater concentrations in macular pigment demonstrated significant improvements in visual function among AMD patients. Collectively, evidence strongly suggests that carotenoid vitamin therapies offer remarkable synergic protection in the neurosensory retina, with the potential to serve as adjunctive nutraceutical therapy in the management of established AMD, albeit these benefits may vary among different stages of disease.

Recent progress in mitochondria-targeting-based nanotechnology for cancer treatment

Mitochondria play critical roles in the regulation of the proliferation and apoptosis of cancerous cells. Nanosystems for targeted delivery of cargos to mitochondria for cancer treatment have attracted increasing attention in the past few years. This review will summarize the state of the art of design and construction of nanosystems used for mitochondria-targeted delivery. The use of nanotechnology for cancer treatment through various pathways such as energy metabolism interference, reactive oxygen species (ROS) regulation, mitochondrial protein targeting, mitochondrial DNA (mtDNA) interference, mitophagy inducing, and combination therapy will be discussed. Finally, the major challenges and an outlook in this field will also be provided.

Chemical Adducts of Reactive Flavor Aldehydes Formed in E-Cigarette Liquids Are Cytotoxic and Inhibit Mitochondrial Function in Respiratory Epithelial Cells

Introduction

Flavor aldehydes in e-cigarettes, including vanillin, ethyl vanillin (vanilla), and benzaldehyde (berry/fruit), rapidly undergo chemical reactions with the e-liquid solvents, propylene glycol, and vegetable glycerol (PG/VG), to form chemical adducts named flavor aldehyde PG/VG acetals that can efficiently transfer to e-cigarette aerosol. The objective of this study was to compare the cytotoxic and metabolic toxic effects of acetals and their parent aldehydes in respiratory epithelial cells.

Aims and Methods

Cell metabolic assays were carried out in bronchial (BEAS-2B) and alveolar (A549) epithelial cells assessing the effects of benzaldehyde, vanillin, ethyl vanillin, and their corresponding PG acetals on key bioenergetic parameters of mitochondrial function. The potential cytotoxic effects of benzaldehyde and vanillin and their corresponding PG acetals were analyzed using the LIVE/DEAD cell assay in BEAS-2B cells and primary human nasal epithelial cells (HNEpC). Cytostatic effects of vanillin and vanillin PG acetal were compared using Click-iT EDU cell proliferation assay in BEAS-2B cells.

Results

Compared with their parent aldehydes, PG acetals diminished key parameters of cellular energy metabolic functions, including basal respiration, adenosine triphosphate production, and spare respiratory capacity. Benzaldehyde PG acetal (1–10 mM) increased cell mortality in BEAS-2B and HNEpC, compared with benzaldehyde. Vanillin PG acetal was more cytotoxic than vanillin at the highest concentration tested while both diminished cellular proliferation in a concentration-dependent manner.

Conclusions

Reaction products formed in e-liquids between flavor aldehydes and solvent chemicals have differential toxicological properties from their parent flavor aldehydes and may contribute to the health effects of e-cigarette aerosol in the respiratory system of e-cigarette users.

Implications

With no inhalation toxicity studies available for acetals, data from this study will provide a basis for further toxicological studies using in vitro and in vivo models. This study suggests that manufacturers’ disclosure of e-liquid ingredients at time of production may be insufficient to inform a comprehensive risk assessment of e-liquids and electronic nicotine delivery systems use, due to the chemical instability of e-liquids over time and the formation of new compounds.

The noncoding-RNA landscape in cardiovascular health and disease

The cardiovascular system plays a pivotal role in regulating and maintaining homeostasis in the human body. Therefore any alteration in regulatory networks that orchestrate heart development as well as adaptation to physiological and environmental stress might result in pathological conditions, which represent the leading cause of death worldwide [1]. The latest advances in genome-wide techniques challenged the "protein-central dogma" with the discovery of the so-called non-coding RNAs (ncRNAs). Despite their lack of protein coding potential, ncRNAs have been largely demonstrated to regulate the majority of biological processes and have also been largely implicated in cardiovascular disorders. This review will first discuss the important mechanistic aspects of some of the classes of ncRNAs such as biogenesis, mechanism of action, as well as their involvement in cardiac diseases. The ncRNA potential uses as therapeutic molecules, with a specific focus on the latest technologies for their in vivo delivery as drug targets, will be described.

A Triphenylphosphonium-Functionalized Mitochondriotropic Nanocarrier for Efficient Co-Delivery of Doxorubicin and Chloroquine and Enhanced Antineoplastic Activity

Drug delivery systems that target subcellular organelles and, in particular, mitochondria are considered to have great potential in treating disorders that are associated with mitochondrial dysfunction, including cancer or neurodegenerative diseases. To this end, a novel hyperbranched mitochondriotropic nanocarrier was developed for the efficient co-delivery of two different (both in chemical and pharmacological terms) bioactive compounds. The carrier is based on hyperbranched poly(ethyleneimine) functionalized with triphenylphosphonium groups that forms ~100 nm diameter nanoparticles in aqueous media and can encapsulate doxorubicin (DOX), a well-known anti-cancer drug, and chloroquine (CQ), a known chemosensitizer with arising potential in anticancer medication. The anticancer activity of this system against two aggressive DOX-resistant human prostate adenocarcinoma cell lines and in in vivo animal studies was assessed. The co-administration of encapsulated DOX and CQ leads to improved cell proliferation inhibition at extremely low DOX concentrations (0.25 μΜ). In vivo experiments against DU145 human prostate cancer cells grafted on immunodeficient mice resulted in tumor growth arrest during the three-week administration period and no pervasive side effects. The findings put forward the potential of such targeted low dose combination treatments as a therapeutic scheme with minimal adverse effects.

Active Targeting of the Nucleus Using Nonpeptidic Boronate Tags

Active intracellular transport is a central mechanism in cell biology, directed by a limited set of naturally occurring signaling peptides. Here, we report the first nonpeptide moiety that recruits intracellular transport machinery for nuclear targeting. Proteins synthetically modified with a simple aromatic boronate motif are actively trafficked to the nucleus via the importin α/β pathway. Significantly, proteins too large to passively diffuse through nuclear pores were readily imported into the nucleus through this boronate-mediated pathway. The use of this simple motif to provide active intracellular targeting provides a promising strategy for directing subcellular localization for therapeutic and fundamental applications.

Integrating Enzymatic Self-Assembly and Mitochondria Targeting for Selectively Killing Cancer Cells without Acquired Drug Resistance

Targeting organelles by modulating the redox potential of mitochondria is a promising approach to kill cancer cells that minimizes acquired drug resistance. However, it lacks selectivity because mitochondria perform essential functions for (almost) all cells. We show that enzyme-instructed self-assembly (EISA), a bioinspired molecular process, selectively generates the assemblies of redox modulators (e.g., triphenyl phosphinium (TPP)) in the pericellular space of cancer cells for uptake, which allows selectively targeting the mitochondria of cancer cells. The attachment of TPP to a pair of enantiomeric, phosphorylated tetrapeptides produces the precursors (L-1P or D-1P) that form oligomers. Upon dephosphorylation catalyzed by ectophosphatases (e.g., alkaline phosphatase (ALP)) overexpressed on cancer cells (e.g., Saos2), the oligomers self-assemble to form nanoscale assemblies only on the surface of the cancer cells. The cancer cells thus uptake these assemblies of TPP via endocytosis, mainly via a caveolae/raft-dependent pathway. Inside the cells, the assemblies of TPP-peptide conjugates escape from the lysosome, induce dysfunction of mitochondria to release cytochrome c, and result in cell death, while the controls (i.e., omitting TPP motif, inhibiting ALP, or removing phosphate trigger) hardly kill the Saos2 cells. Most importantly, the repeated stimulation of the cancers by the precursors, unexpectedly, sensitizes the cancer cells to the precursors. As the first example of the integration of subcellular targeting with cell targeting, this study validates the spatial control of the assemblies of nonspecific cytotoxic agents by EISA as a promising molecular process for selectively killing cancer cells without inducing acquired drug resistance.

A Dual-Ligand Liposomal System Composed of a Cell-Penetrating Peptide and a Mitochondrial RNA Aptamer Synergistically Facilitates Cellular Uptake and Mitochondrial Targeting

It has been reported that the use of mitochondrial RNA aptamers including RNase P (RP) results in the selective mitochondrial delivery of endogenous and exogenous RNAs. The issue of whether these aptamers would be useful ligands for the mitochondrial targeting of a nanoparticle has not been demonstrated to date because nanocarriers modified with these RNA aptamers are insufficiently internalized by cells. We report here on the development of a dual-ligand liposomal system composed of octaarginine (R8), a device that enhances cellular uptake, and an RP aptamer for mitochondrial targeting to permit a nanocarrier to be efficiently delivered to mitochondria. Surprisingly, the cellular uptake of the R8-modified nanocarrier was facilitated by modification with an RP aptamer. The optimal composition of a nanocarrier needed for efficient cellular uptake and mitochondrial targeting was determined. In a confocal laser scanning microscopy analysis, the dual-ligand-modified nanocarrier was found to result in effective mitochondrial targeting through an ATP-dependent pathway and was much more effective than a single-ligand R8-modified nanocarrier. This is the first report of the regulation of intracellular trafficking by a mitochondrial RNA aptamer-modified nanocarrier system.

Design, Synthesis and In Vitro Activity of Anticancer Styrylquinolines. The p53 Independent Mechanism of Action

A group of styrylquinolines were synthesized and tested for their anti-proliferative activity. Anti-proliferative activity was evaluated against the human colon carcinoma cell lines that had a normal expression of the p53 protein (HCT116 p53^+/+) and mutants with a disabled TP53 gene (HCT116 p53^-/-) and against the GM 07492 normal human fibroblast cell line. A SAR study revealed the importance of Cl and OH as substituents in the styryl moiety. Several of the compounds that were tested were found to have a marked anti-proliferative activity that was similar to or better than doxorubicin and were more active against the p53 null than the wild type cells. The cellular localization tests and caspase activity assays suggest a mechanism of action through the mitochondrial pathway of apoptosis in a p53-independent manner. The activity of the styrylquinoline compounds may be associated with their DNA intercalating ability.

Nanoparticle Uptake: The Phagocyte Problem

Phagocytes are key cellular participants determining important aspects of host exposure to nanomaterials, initiating clearance, biodistribution and the tenuous balance between host tolerance and adverse nanotoxicity. Macrophages in particular are believed to be among the first and primary cell types that process nanoparticles, mediating host inflammatory and immunological biological responses. These processes occur ubiquitously throughout tissues where nanomaterials are present, including the host mononuclear phagocytic system (MPS) residents in dedicated host filtration organs (i.e., liver, kidney spleen, and lung). Thus, to understand nanomaterials exposure risks it is critical to understand how nanomaterials are recognized, internalized, trafficked and distributed within diverse types of host macrophages and how possible cell-based reactions resulting from nanomaterial exposures further inflammatory host responses in vivo. This review focuses on describing macrophage-based initiation of downstream hallmark immunological and inflammatory processes resulting from phagocyte exposure to and internalization of nanomaterials.

Honokiol blocks and reverses cardiac hypertrophy in mice by activating mitochondrial Sirt3

Honokiol (HKL) is a natural biphenolic compound derived from the bark of magnolia trees with anti-inflammatory, anti-oxidative, anti-tumor and neuroprotective properties. Here we show that HKL blocks agonist-induced and pressure overload-mediated, cardiac hypertrophic responses, and ameliorates pre-existing cardiac hypertrophy, in mice. Our data suggest that the anti-hypertrophic effects of HKL depend on activation of the deacetylase SIRT3. We demonstrate that HKL is present in mitochondria, enhances SIRT3 expression nearly two-fold and suggest that HKL may bind to SIRT3 to further increase its activity. Increased SIRT3 activity is associated with reduced acetylation of mitochondrial SIRT3 substrates, MnSOD and OSCP. HKL-treatment increases mitochondrial rate of oxygen consumption and reduces ROS synthesis in wild-type, but not in SIRT3-KO cells. Moreover, HKL-treatment blocks cardiac fibroblast proliferation and differentiation to myofibroblasts in SIRT3-dependent manner. These results suggest that HKL is a pharmacological activator of SIRT3 capable of blocking, and even reversing, the cardiac hypertrophic response.

Targeting molecular hydrogen to mitochondria: barriers and gateways

Although the administration of molecular hydrogen (H2, dihydrogen) has been recognized as an effective innovative therapeutic procedure in biomedicine, H2 cellular kinetics and utilization seems to be less understood. In particular, mitochondrial barriers might impact on H2 use in mitochondria-related diseases and conditions. Double-membrane organization of mitochondria and large membrane potential are important elements of mitochondrial stability that control the transport of the molecule into and out of the organelle. In this perspective paper, we advanced possible obstacles and advantages for H2 delivery to mitochondria.

Gemini surfactants mediate efficient mitochondrial gene delivery and expression

Gene delivery targeting mitochondria has the potential to transform the therapeutic landscape of mitochondrial genetic diseases. Taking advantage of the nonuniversal genetic code used by mitochondria, a plasmid DNA construct able to be specifically expressed in these organelles was designed by including a codon, which codes for an amino acid only if read by the mitochondrial ribosomes. In the present work, gemini surfactants were shown to successfully deliver plasmid DNA to mitochondria. Gemini surfactant-based DNA complexes were taken up by cells through a variety of routes, including endocytic pathways, and showed propensity for inducing membrane destabilization under acidic conditions, thus facilitating cytoplasmic release of DNA. Furthermore, the complexes interacted extensively with lipid membrane models mimicking the composition of the mitochondrial membrane, which predicts a favored interaction of the complexes with mitochondria in the intracellular environment. This work unravels new possibilities for gene therapy toward mitochondrial diseases.

Peptide-based carbon nanotubes for mitochondrial targeting

In the present study, we report the design and synthesis of peptide-based-multi-walled carbon nanotubes (MWCNTs) to target mitochondria. Targeting these intracellular organelles might open the way to develop alternative systems to address diseases related to genetic mutations in mitochondrial (mt)-DNA, by delivering therapeutic oligonucleotides. The first step towards mitochondrial delivery of this type of nucleic acid was to target MWCNTs to mitochondria by covalent functionalization with a well-known endogenous mitochondrial targeting sequence (MTS). The subcellular localization of the conjugates, which were fluorescently labeled, in murine RAW 264.7 macrophages and human HeLa cells was then studied using different microscopy techniques, such as wide-field epifluorescence microscopy, confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). The localization of the MTS-MWCNT conjugates into mitochondria was further confirmed by analyzing the isolated organelles using TEM.

Alkyne-azide "click" chemistry in designing nanocarriers for applications in biology

The alkyne-azide cycloaddition, popularly known as the "click" reaction, has been extensively exploited in molecule/macromolecule build-up, and has offered tremendous potential in the design of nanomaterials for applications in a diverse range of disciplines, including biology. Some advantageous characteristics of this coupling include high efficiency, and adaptability to the environment in which the desired covalent linking of the alkyne and azide terminated moieties needs to be carried out. The efficient delivery of active pharmaceutical agents to specific organelles, employing nanocarriers developed through the use of "click" chemistry, constitutes a continuing topical area of research. In this review, we highlight important contributions click chemistry has made in the design of macromolecule-based nanomaterials for therapeutic intervention in mitochondria and lipid droplets.

Toward intracellular targeted delivery of cancer therapeutics: progress and clinical outlook for brain tumor therapy

A number of anti-cancer drugs have their targets localized to particular intracellular compartments. These drugs reach the targets mainly through diffusion, dependent on biophysical and biochemical forces that allow cell penetration. This means that both cancer cells and normal cells will be subjected to such diffusion; hence many of these drugs, like chemotherapeutics, are potentially toxic and the concentration achieved at the site of their action is often suboptimal. The same relates to radiation that indiscriminately affects normal and diseased cells. However, nature-designed systems enable compounds present in the extracellular environment to end up inside the cell and even travel to more specific intracellular compartments. For example, viruses and bacterial toxins can more or less specifically recognize eukaryotic cells, enter these cells, and direct some protein portions to designated intracellular areas. These phenomena have led to creative thinking, such as employing viruses or bacterial toxins for cargo delivery to cells and, more specifically, to cancer cells. Proteins can be genetically engineered in order to not only mimic what viruses and bacterial toxins can do, but also to add new functions, extending or changing the intracellular routes. It is possible to make conjugates or, more preferably, single-chain proteins that recognize cancer cells and deliver cargo inside the cells, even to the desired subcellular compartment. These findings offer new opportunities to deliver drugs/labels only to cancer cells and only to their site of action within the cells. The development of such dual-specificity vectors for targeting cancer cells is an attractive and potentially safer and more efficacious way of delivering drugs. We provide examples of this approach for delivering brain cancer therapeutics, using a specific biomarker on glioblastoma tumor cells.

Controlling subcellular delivery to optimize therapeutic effect

This article focuses on drug targeting to specific cellular organelles for therapeutic purposes. Drugs can be delivered to all major organelles of the cell (cytosol, endosome/lysosome, nucleus, nucleolus, mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes and proteasomes) where they exert specific effects in those particular subcellular compartments. Delivery can be achieved by chemical (e.g., polymeric) or biological (e.g., signal sequences) means. Unidirectional targeting to individual organelles has proven to be immensely successful for drug therapy. Newer technologies that accommodate multiple signals (e.g., protein switch and virus-like delivery systems) mimic nature and allow for a more sophisticated approach to drug delivery. Harnessing different methods of targeting multiple organelles in a cell will lead to better drug delivery and improvements in disease therapy.

A molecular carrier to transport and deliver cisplatin into endometrial cancer cells

The leader peptide of a recombinant manganese superoxide dismutase (rMnSOD-Lp) acts as a molecular carrier. Clonogenic tests on normal (MRC-5) and endometrial adenocarcinoma cells (HTB-112) were carried out in the presence of rMnSOD-Lp, cisplatin alone (CC) or cisplatin conjugated to the rMnSOD-Lp (rMnSOD-Lp-CC). The platinum delivered into the cells was measured by atomic spectrophotometric absorbance. The treatments on tumor and normal cells were finally evaluated by LM and TM microscopy. Tumor cell death in the case of 0.5 μM cisplatin on its own was minimal, while in the presence of 0.5 μM rMnSOD-Lp-CC, no tumor cells survived. Atomic absorbance analysis showed that rMnSOD-Lp-CC delivered approximately four times more cisplatin into HTB-112 cells than the amount delivered using cisplatin alone. By LM observation, the cells treated with rMnSOD-Lp-CC showed signs of nuclear and cytoplasmic fragmentation, that is, apoptosis induced by the treatment. The therapeutic effect of rMnSOD-Lp-CC on endometrial cancer cells was significant, while on the normal cells it showed only a minimal toxicity. We believe that rMnSOD-Lp deserves to be considered as a molecular carrier to deliver cisplatin directly into tumor cells, thus transforming its antireplicative activity into a specific and selective antitumor agent.

Intracellular delivery of redox cycler-doxorubicin to the mitochondria of cancer cell by folate receptor targeted mitocancerotropic liposomes

Cancer cells reflect higher level of ROS in comparison to the normal cell, so they become more vulnerable to further oxidative stress induced by exogenous ROS-generating agents. Through this a novel therapeutic strategy has evolved, which involves the delivery of redox cycler-doxorubicin (DOX) to the mitochondria of cancer cell where it acts as a source of exogenous ROS production. The purpose of this study is to develop a liposomal preparation which exhibits a propensity to selectively target cancer cell along with the potential of delivering drug to mitochondria of cell. We have rendered liposomes mitocancerotropic (FA-MTLs) by their surface modification with dual ligands, folic acid (FA) for cancer cell targeting and triphenylphosphonium (TPP) cations for mitochondria targeting. The cytotoxicity, ROS production and cell uptake of doxorubicin loaded liposomes were evaluated in FR (+) KB cells and found to be increased considerably with FA-MTLs in comparison to folic acid appended, mitochondria targeted and non-targeted liposomes. As confirmed by confocal microscopy, the STPP appended liposomes delivered DOX to mitochondria of cancer cell and also showed higher ROS production and cytotoxicity in comparison to folic acid appended and non-targeted liposomes. Most importantly, mitocancerotropic liposomes showed superior activity over mitochondria targeted liposomes which confirm the synergistic effect imparted by the presence of dual ligands - folic acid and TPP on the enhancement of cellular and mitochondrial delivery of doxorubicin in KB cells.

Delivery of bioactive molecules to the mitochondrial genome using a membrane-fusing, liposome-based carrier, DF-MITO-Porter

Mitochondrial dysfunction has been implicated in a variety of human diseases. It is now well accepted that mutations and defects in the mitochondrial genome form the basis of these diseases. Therefore, mitochondrial gene therapy and diagnosis would be expected to have great medical benefits. To achieve such a strategy, it will be necessary to deliver therapeutic agents into mitochondria in living cells. We report here on an approach to accomplish this via the use of a Dual Function (DF)-MITO-Porter, aimed at the mitochondrial genome, so-called mitochondrial DNA (mtDNA). The DF-MITO-Porter, a nano carrier for mitochondrial delivery, has the ability to penetrate the endosomal and mitochondrial membranes via step-wise membrane fusion. We first constructed a DF-MITO-Porter encapsulating DNase I protein as a bioactive cargo. It was expected that mtDNA would be digested, when the DNase I was delivered to the mitochondria. We observed the intracellular trafficking of the carriers, and then measured mitochondrial activity and mtDNA-levels after the delivery of DNase I by the DF-MITO-Porter. The findings confirm that the DF-MITO-Porter effectively delivered the DNase I into the mitochondria, and provides a demonstration of its potential use in therapies that are selective for the mitochondrial genome.

Mitochondrial dysfunction in retinal diseases

The mitochondrion is a vital intracellular organelle for retinal cell function and survival. There is growing confirmation to support an association between mitochondrial dysfunction and a number of retinal degenerations. Investigations have also unveiled mitochondrial genomic instability as one of the contributing factors for age-related retinal pathophysiology. This review highlights the role of mitochondrial dysfunction originating from oxidative stress in the etiology of retinal diseases including diabetic retinopathy, glaucoma and age-related macular degeneration (AMD). Moreover, mitochondrial DNA (mtDNA) damage associated with AMD due to susceptibility of mtDNA to oxidative damage and failure of mtDNA repair pathways is also highlighted in this review. The susceptibility of neural retina and retinal pigment epithelium (RPE) mitochondria to oxidative damage with ageing appears to be a major factor in retinal degeneration. It thus appears that the mitochondrion is a weak link in the antioxidant defenses of retinal cells. In addition, failure of mtDNA repair pathways can also specifically contribute towards pathogenesis of AMD. This review will further summarize the prospective role of mitochondria targeting therapeutic agents for the treatment of retinal disease. Mitochondria based drug targeting to diminish oxidative stress or promote repair of mtDNA damage may offer potential alternatives for the treatment of various retinal degenerative diseases.

A novel mitotropic oligolysine nanocarrier: Targeted delivery of covalently bound D-Luciferin to cell mitochondria

New and emerging therapeutic approaches focus on the targeted delivery of therapeutic agents to cell mitochondria with high specificity. Herein we present a novel mitotropic nanocarrier based on an oligolysine scaffold by addition of two triphenylphosphonium cations per oligomer. Although the parent oligolysine failed to enter healthy cells, the triphenylphosphonium modified carrier, with or without D-Luciferin, attached as cargo molecule, demonstrated striking mitochondrial specificity. Furthermore, the oligolysine bound d-Luciferin exhibited chemiluminescence, of lower intensity than free d-Luciferin, yet of remarkably longer steady-state temporal profile.

Dual function MITO-Porter, a nano carrier integrating both efficient cytoplasmic delivery and mitochondrial macromolecule delivery

Mitochondrial dysfunction is associated with a variety of human diseases including inherited mitochondrial diseases, neurodegenerative disorders, diabetes mellitus, and cancer. Effective medical therapies for mitochondrial diseases will ultimately require an optimal drug delivery system, which will likely be achieved through innovations in the nanotechnology of intracellular trafficking. To achieve efficient mitochondrial drug delivery, two independent processes, i.e., "cytoplasmic delivery through the cell membrane" and "mitochondrial delivery through the mitochondrial membrane" are required. In previous studies, we developed an octaarginine (R8) modified nano carrier for efficient cytoplasmic delivery, showing that R8-modified liposomes were internalized into cells efficiently. On the other hand, we also constructed MITO-Porter for the mitochondrial delivery of macromolecules, a liposome-based carrier that delivers cargos to mitochondria via membrane fusion. Here, we report the development of a dual function MITO-Porter (DF-MITO-Porter), based on the concept of integrating both R8-modified liposomes and MITO-Porter. We show that the DF-MITO-Porter effectively delivers exogenous macro-biomolecules into the mitochondrial matrix, and provide a demonstration of its potential use in therapies aimed at mitochondrial DNA.

Receptor-targeted nanocarriers for therapeutic delivery to cancer

Efficient and site-specific delivery of therapeutic drugs is a critical challenge in clinical treatment of cancer. Nano-sized carriers such as liposomes, micelles, and polymeric nanoparticles have been investigated for improving bioavailability and pharmacokinetic properties of therapeutics via various mechanisms, for example, the enhanced permeability and retention (EPR) effect. Further improvement can potentially be achieved by conjugation of targeting ligands onto nanocarriers to achieve selective delivery to the tumour cell or the tumour vasculature. Indeed, receptor-targeted nanocarrier delivery has been shown to improve therapeutic responses both in vitro and in vivo. A variety of ligands have been investigated including folate, transferrin, antibodies, peptides and aptamers. Multiple functionalities can be incorporated into the design of nanoparticles, e.g., to enable imaging and triggered intracellular drug release. In this review, we mainly focus on recent advances on the development of targeted nanocarriers and will introduce novel concepts such as multi-targeting and multi-functional nanoparticles.

Strategies in the design of nanoparticles for therapeutic applications

Engineered nanoparticles have the potential to revolutionize the diagnosis and treatment of many diseases; for example, by allowing the targeted delivery of a drug to particular subsets of cells. However, so far, such nanoparticles have not proved capable of surmounting all of the biological barriers required to achieve this goal. Nevertheless, advances in nanoparticle engineering, as well as advances in understanding the importance of nanoparticle characteristics such as size, shape and surface properties for biological interactions, are creating new opportunities for the development of nanoparticles for therapeutic applications. This Review focuses on recent progress important for the rational design of such nanoparticles and discusses the challenges to realizing the potential of nanoparticles.

New benzophenone-derived bisphosphonium salts as leishmanicidal leads targeting mitochondria through inhibition of respiratory complex II

A set of benzophenone-derived bisphosphonium salts was synthesized and assayed for lethal activity on the human protozoan parasite Leishmania. A subset of them, mostly characterized by phosphonium substituents with an intermediate hydrophobicity, inhibited parasite proliferation at low micromolar range of concentrations. The best of this subset, 4,4'-bis((tri-n-pentylphosphonium)methyl)benzophenone dibromide, showed a very scarce toxicity on mammalian cells. This compound targets complex II of the respiratory chain of the parasite, based on (i) a dramatically swollen mitochondrion in treated parasites, (ii) fast decrease of cytoplasmic ATP, (iii) a decrease of the electrochemical mitochondrial potential, and (iv) inhibition of the oxygen consumption rate using succinate as substrate. Thus, this type of compounds represents a new lead in the development of leishmanicidal drugs.

Reactive oxygen and nitrogen species in normal physiological processes

Abstract Reactive oxygen species (ROS) and reactive nitrogen species have generally been considered as being highly reactive and cytotoxic molecules. Besides their noxious effects, ROS participate in physiological processes in a carefully regulated manner. By way of example, microbicidal ROS are produced in professional phagocytes, ROS function as short-lived messengers having a role in signal transduction and, among other processes, participate in the synthesis of the iodothyronine hormones, reproduction, apoptosis and necrosis. Because of their ability to mediate a crosstalk between key molecules, their role might be dual (at least in some cases). The levels of ROS increase from a certain age, being associated with various diseases typical of senescence. The aim of this review is to summarize the recent findings on the physiological role of ROS. Other issues addressed are an increase in ROS levels during ageing, and the possibility of the physiological nature of this process.

Interaction of gold nanoparticles with mitochondria

Mitochondrion is one of the most important organelles in cells with several vital responsibilities. The consequence of a deficiency in the function of mitochondrion could result with the wide range of diseases and disorders. In this study, we investigated the feasibility of utilizing surface-enhanced Raman scattering (SERS) to understand the mode of interaction of gold nanoparticles (GNPs) with mitochondria. The living lung cancer cells and the isolated mitochondria from these cells were treated with gold colloidal suspension for SERS experiments. The AFM images of the mitochondria confirmed that the treatment did not cause substantial damage to mitochondria. The localization of GNPs in living cells is investigated with confocal microscopy and found that GNPs form aggregates in the cytosol away from the mitochondria. However, SERS spectra obtained from isolated mitochondria and living cells indicate that GNPs escaped from the endosomes or entered into the living cell through another route may be in contact with mitochondria in a living cell. The findings of this study indicate that SERS can be used for mitochondrial research.

Mitochondrial drug delivery systems for macromolecule and their therapeutic application to mitochondrial diseases

Mitochondrial dysfunction has been implicated in a variety of human disorders--the so-called mitochondrial diseases. Therefore, the organelle is a promising therapeutic drug target. In this review, we describe the key role of mitochondria in living cells, a number of mitochondrial drug delivery systems and mitochondria-targeted therapeutic strategies. In particular, we discuss mitochondrial delivery of macromolecules, such as proteins and nucleic acids. The discussion of protein delivery is limited primarily to the mitochondrial import machinery. In the section on mitochondrial gene delivery and therapy, we discuss mitochondrial diseases caused by mutations in mitochondrial DNA, several gene delivery strategies and approaches to mitochondrial gene therapy. This review also summarizes our current efforts regarding liposome-based delivery system including use of a multifunctional envelope-type nano-device (MEND) and mitochondrial liposome-based delivery as anti-cancer therapies. Furthermore, we introduce the novel MITO-Porter--a liposome-based mitochondrial delivery system that functions using a membrane-fusion mechanism.

Carrier-mediated cellular uptake of pharmaceutical drugs: an exception or the rule?

It is generally thought that many drug molecules are transported across biological membranes via passive diffusion at a rate related to their lipophilicity. However, the types of biophysical forces involved in the interaction of drugs with lipid membranes are no different from those involved in their interaction with proteins, and so arguments based on lipophilicity could also be applied to drug uptake by membrane transporters or carriers. In this article, we discuss the evidence supporting the idea that rather than being an exception, carrier-mediated and active uptake of drugs may be more common than is usually assumed - including a summary of specific cases in which drugs are known to be taken up into cells via defined carriers - and consider the implications for drug discovery and development.