Cationic bolasomes with delocalized charge centers as mitochondria-specific DNA delivery systems

2-N-Methyl modifications and SAR studies of manzamine A

Quaternary carbolinium salts have been reported to show improved antimalarial activity and reduced cytotoxicity as compared to electronically neutral beta-carbolines. In this study, mono- and di-methylated quaternary carbolinium cations of manzamine A were synthesized and evaluated for their in vitro antimalarial and antimicrobial activity, cytotoxicity, and also their potential for glycogen synthase kinase (GSK-3beta) inhibition using molecular docking studies. Among the analogs, 2-N-methylmanzamine A (2) exhibited antimalarial activity (IC(50) 0.7-1.0microM) but was less potent than manzamine A. However the compound was significantly less cytotoxic to mammalian kidney fibroblasts and the selectivity index was in the same range as manzamine A.

Polymers and nanoparticles: Intelligent tools for intracellular targeting?

In recent years, a new generation of drugs has entered the pharmaceutical market. Some are more potent, but some are also more toxic and thus, therapeutical efficacy may be hindered, and severe side effects may be observed, unless they are delivered to their assigned place of effect. Those targets are not only certain cell types, moreover, in cancer therapy for example, some drugs even have to be targeted to a specific cell organelle. Those targets in eukaryotic cells include among others endo- and lysosomes, mitochondria, the so-called power plants of the cells, and the biggest compartment with almost all the genetic information, the nucleus. In this review, we describe how the drugs can be directed to specific subcellular organelles and focus especially on synthetic polymers and nanoparticles as their carriers. Furthermore, we portray the progress that has been accomplished in recent years in the field of designing the carriers for efficient delivery into these target structures. Yet, we do not fail to mention the obstacles that still exist and are preventing polymeric and nanoparticular drug carrier systems from their broad application in humans.

MITO-Porter: A liposome-based carrier system for delivery of macromolecules into mitochondria via membrane fusion

Mitochondria are the principal producers of energy in higher cells. Mitochondrial dysfunction is implicated in a variety of human diseases, including cancer and neurodegenerative disorders. Effective medical therapies for such diseases will ultimately require targeted delivery of therapeutic proteins or nucleic acids to the mitochondria, which will be achieved through innovations in the nanotechnology of intracellular trafficking. Here we describe a liposome-based carrier that delivers its macromolecular cargo to the mitochondrial interior via membrane fusion. These liposome particles, which we call MITO-Porters, carry octaarginine surface modifications to stimulate their entry into cells as intact vesicles (via macropinocytosis). We identified lipid compositions for the MITO-Porter which promote both its fusion with the mitochondrial membrane and the release of its cargo to the intra-mitochondrial compartment in living cells. Thus, the MITO-Porter holds promise as an efficacious system for the delivery of both large and small therapeutic molecules into mitochondria.

Mitochondriotropics: A review of their mode of action, and their applications for drug and DNA delivery to mammalian mitochondria

Since compounds targeting mitochondria exhibit diverse accumulation mechanisms and chemical features, various questions arise. Do such "mitochondriotropics" have a characteristic chemistry? What are mitochondrial uptake mechanisms? Do mitochondriotropics necessarily accumulate in mitochondria or merely have access? Is the concept "mitochondriotropic" of any practical value? To seek answers, a non-biased sample of >100 mitochondriotropics was generated from the review literature. This dataset was examined using: physicochemical classification; quantitative structure-activity relations (QSAR) models; and a Fick-Nernst-Planck physicochemical model. The ability of the latter two approaches to predict mitochondriotropic behaviour was assessed, and comparisons made between methods, and with current assumptions. All approaches provided instructive pictures of the nature of mitochondriotropics. Thus although lipophilic cations are regarded as the commonest structural type, only a third were such. Much the same proportion were acids, potentially or actually anions. Many mitochondriotropics were electrically neutral compounds. All categorizations involved overall molecular properties, not the presence of "mitochondriotropic tags"--again contrary to literature concepts. Selective mitochondrial accumulation involved electric potential, ion-trapping, and complex formation with cardiolipin; non-specific accumulation involved membrane partitioning. Non-specific access required only low lipophilicity. Mitochondrial targeting did not preclude additional accumulation sites, e.g. lysosomes. The concept "mitochondriotropic" remains useful, although may imply access, not accumulation. QSAR and Fick-Nernst-Planck approaches are complementary--neither is universally applicable. Using both approaches enabled the mitochondriotropic behavior of >80% of the dataset to be predicted, and the physicochemistry of mitochondriotropics to be specified in some detail. This can facilitate guided syntheses and selection of optimal mitochondriotropic structures.

Mitochondria-specific nanotechnology

Mitochondrial research has made an enormous leap since mitochondrial DNA mutations were identified as a primary cause for human diseases in 1988 and the organelle’s crucial role in apoptosis was identified during the 1990s. Considerable progress has been made in identifying the molecular components of the mitochondrial machinery responsible for life and cell death; however, effective therapies for diseases caused by mitochondrial dysfunction remain elusive. An impediment to manipulating, probing and assessing the functional components of mammalian mitochondria within living cells is their limited accessibility to direct physical, biochemical and pharmacological manipulation. Recent advances in nanotechnology hold the promise of helping to overcome these obstacles. New tools will undoubtedly emerge, creating new avenues for the diagnosis and therapy of mitochondrial disorders. This review briefly discusses current efforts to merge nanobiotechnology with mitochondrial medicine.

DNA delivery to the mitochondria sites using mitochondrial leader peptide conjugated polyethylenimine

Some genetic diseases are associated with the defects of the mitochondrial genome. Direct DNA delivery to the mitochondrial matrix has been suggested as an approach for mitochondrial gene therapy for these diseases. We hypothesized that a mitochondrial leader peptide (LP) conjugated polyethylenimine (PEI) could deliver DNA to the mitochondrial sites. PEI-LP was synthesized by the conjugation of LP to PEI using disulfide bond. The complex formation of PEI-LP with DNA was confirmed by a gel retardation assay. In this study, DNA was completely retarded at a 0.4/1 PEI-LP/DNA weight ratio. In vitro delivery tests into isolated mitochondria or living cells were performed with rhodamin-labeled DNA and PEI-LP. In vitro cell-free delivery assay with isolated mitochondria showed that PEI-LP/DNA complexes were localized at mitochondria sites. Furthermore, the PEL-LP/DNA complexes were localized at the mitochondrial sites in living cells. However, a control carrier, PEI, did not show this effect. In addition, MTT assay showed that PEI-LP showed lower cytotoxicity than PEI. These results suggest that PEI-LP can deliver DNA to the mitochondrial sites and may be useful for the development of mitochondrial gene therapy.

Gene therapy of the other genome: the challenges of treating mitochondrial DNA defects

Human mitochondrial DNA is a 16.5 kb circular DNA molecule located inside the mitochondrial matrix. Although accounting for only about 1% of total cellular DNA, defects in mitochondrial DNA have been found to have major effects on human health. A single mtDNA mutation may cause a bewildering variety of clinical symptoms mainly involving the neuromuscular system at any age of onset. Despite significant advances in the understanding of mitochondrial DNA defects at a molecular level, the clinical diagnosis of mtDNA diseases remains a significant challenge and effective therapies for such diseases are as yet unavailable. In contrast to gene therapy for chromosomal DNA defects, mitochondrial gene therapy is a field that is still in its infancy and attempts towards gene therapy of the mitochondrial genome are rare. In this review we outline what we believe are the unique challenges associated with the correction of mtDNA mutations and summarize current approaches to gene therapy for the "other genome".

Mitochondrial drug delivery and mitochondrial disease therapy--an approach to liposome-based delivery targeted to mitochondria

Recent progress in genetics and molecular biology has provided useful information regarding the molecular mechanisms associated with the mitochondrial diseases. Genetic approaches were initiated in the late 1980s to clarify the gene responsible for various mitochondrial diseases, and information concerning genetic mutations is currently used in the diagnosis of mitochondrial diseases. Moreover, it was also revealed that mitochondria play a central role in apoptosis, or programmed cell death, which is closely related to the loss of physiological functions of tissues. Therefore, drug therapies targeted to the mitochondria would be highly desirable. In spite of the huge amount of mechanism-based studies of mitochondrial diseases, effective therapies have not yet been established mainly because of the lack of an adequate delivery system. To date, numerous investigators have attempted to establish a mitochondrial drug delivery system. However, many problems remain to be overcome before a clinical application can be achieved. To fulfill a drug delivery targeted to mitochondria, we first need to establish a method to encapsulate various drugs, proteins, peptides, and genes into a drug carrier depending on their physical characteristics. Second, we need to target it to a specific cell. Finally, multi-processes of intracellular trafficking should be sophisticatedly regulated so as to release a drug carrier from the endosome to the cytosol, and thereafter to deliver to the mitochondria. In this review, we describe the current state of the development of mitochondrial drug delivery systems, and discuss the advantage and disadvantage of each system. Our current efforts to develop an efficient method for the packaging of macromolecules and regulating intracellular trafficking are also summarized. Furthermore, novel concept of "Regulation of intramitochondrial trafficking" is proposed herein as a future challenge to the development of a mitochondrial drug delivery system.

Recent approaches to intracellular delivery of drugs and DNA and organelle targeting

Intracellular delivery of various drugs, including DNA, and drug carriers can sharply increase the efficiency of various treatment protocols. However, the receptor-mediated endocytosis of drugs, drug carriers, and DNA results in their lysosomal delivery and significant degradation. The problem can be solved and therapy efficacy still further increased if the approaches for direct intracytoplasmic delivery that bypass the endocytic pathway are developed. This is especially important for many anticancer drugs (proapoptotic drugs whose primary action site is the mitochondrial membrane) and gene therapy (nuclear or mitochondrial genomes should be targeted). This review considers several current approaches for intracellular drug delivery: the use of pH-sensitive liposomes, the use of cell-penetrating proteins and peptides, and the use of immunoliposomes targeting intracellular antigens. Among intracellular targets, nuclei (gene therapy), mitochondria (proapoptotic cancer therapy and targeting of the mitochondrial genome), and lysosomes (lysosomal targeting of enzymes for the therapy of the lysosomal storage diseases) are considered. Examples of successful intracellular and organelle-specific delivery of biologically active molecules, including DNA, are presented; unanswered questions, challenges, and future trends are also discussed.

Synthesis of three classes of rhodacyanine dyes and evaluation of their in vitro and in vivo antimalarial activity

Selected members of three classes of rhodacyanine dyes, [0,0]-, [1,0]-, and [0,0,0]-rhodacyanines, were synthesized and their in vitro antimalarial activities against Plasmodium falciparum K1 (chloroquine-resistant strain) as well as their in vivo activities against P. berghei in mice were determined. The novel [0,0,0]-rhodacynines, 3e and 3h, possessing a benzothiazole moiety, were shown to have highly promising antimalarial activities in vivo. Moreover, the [0,0,0]-rhodacyanines were found to be orally bioavailable.

Lipophilic triphenylphosphonium cations as tools in mitochondrial bioenergetics and free radical biology

Lipophilic phosphonium cations were first used to investigate mitochondrial biology by Vladimir Skulachev and colleagues in the late 1960s. Since then, these molecules have become important tools for exploring mitochondrial bioenergetics and free radical biology. Here we review why these molecules are useful in mitochondrial research and outline some of the ways in which they are now being utilized.

Induction of petite mutants in yeast Saccharomyces cerevisiae by the anticancer drug dequalinium

Dequalinium (DEQ), a drug with both antimicrobial and anticancer activity, induced the formation of petite (respiration-deficient) mutants in the yeast Saccharomyces cerevisiae. DEQ was found to be approximately 50-fold more potent than ethidium bromide (EB) at inducing petites. Analysis of the DEQ-induced petite mutants indicated a complete loss of mitochondrial DNA (<1 copy/cell). Prior to the loss of mtDNA, DEQ caused cleavage of the mtDNA into a population of fragments 30-40kbp in size suggesting that this drug causes petites by inducing a breakdown of mtDNA. The selective effect of DEQ on yeast mtDNA may underlie the antifungal activity of this chemotherapeutic agent.

Targeted drug delivery to mammalian mitochondria in living cells

Mitochondrial dysfunction causes or contributes to a large number of human disorders including neuromuscular and neurodegenerative diseases, diabetes, ischaemia-reperfusion injury and cancer. Increasing efforts are being made towards mitochondria-directed pharmacological intervention, leading to the emergence of 'mitochondrial medicine' as a new field of biomedical research. The identification of new molecular mitochondrial drug targets in combination with the development of methods for selectively delivering biologically active molecules to the site of mitochondria will eventually launch new therapies for the treatment of mitochondria-related diseases, based either on the selective protection, repair or eradication of cells. This review discusses the need for the development of mitochondria-specific drug and DNA delivery systems, and evaluates the currently employed strategies for mitochondrial drug targeting, including some of their potential therapeutic applications.

Synthesis and Evaluation of β-Carbolinium Cations as New Antimalarial Agents Based on π-Delocalized Lipophilic Cation (DLC) Hypothesis

Several beta-carbolines including naturally occurring substances and their corresponding cationic derivatives were synthesized and evaluated for antimalarial (antiplasmodial) activity in vitro and in vivo. A tetracyclic carbolinium salt was elucidated for antileishmanial and antitrypanosomal activities in vitro as well as antiplasmodial activity. Quarternary carbolinium cations showed much higher potencies in vitro than electronically neutral beta-carbolines and a good correlation was observed between pi-delocalized lipophilic cationic (DLC) structure and antimalarial efficacy. beta-Carbolinium compounds exhibit medium suppressive activity in vivo against rodent malaria.

Strategies for treating disorders of the mitochondrial genome

Defects of the mitochondrial genome are a significant cause of disease. Patients suffer from a wide variety of clinical presentations, ranging from fatal infantile disease to mild muscle weakness. Most disorders, however, are characterized by inexorable progression. As mutations often cause defects in several components of the complexes that couple oxidative phosphorylation, this terminal state of oxidative metabolism cannot be readily bypassed by dietary means, leading to the search for novel therapies. In this article, we present the theory behind several concepts and report progress. We also discuss some of the recent difficulties encountered in the progress towards an antigenomc approach to treating mtDNA disorders.

New Trends in Biomedical Aging Research

BACKGROUND

The increasing demand for health care services, the extraordinary results obtained by applying innovative biotechnology, and the intense debate aroused by the possibility that postponement of aging may be in sight should promote public enthusiasm and funding for biomedical aging research aimed at enhancing a healthy life span by healthy productive life.

OBJECTIVE

New trends in biomedical aging research arise from the advancement of knowledge on the basic molecular mechanisms of aging and the availability of advanced biotechnology.

RESULTS

The emerging scenario is that, in opposition to the highly publicized, yet unwarranted claims of existing so-called anti-aging treatments, innovative and promising therapies for the treatment and prevention of age-related diseases and intriguing strategies aimed at the postponement of aging are currently in the process of development.

CONCLUSIONS

Although many problems will remain unsolved for long, it seems that a common consensus has been raised towards the possible serious impact of these strategies on the development of knowledge around the mechanisms of aging.

π-Delocalized β-carbolinium cations as potential antimalarials

Several beta-carboline compounds including natural products and their corresponding salts were synthesized and evaluated for antimalarial activity and cytotoxicity levels. Quaternary carbolinium cations showed much higher potencies than neutral beta-carbolines and a good correlation was observed between pi-delocalized lipophilic cationic structure and antimalarial efficacy.

Mitochondrial pharmaceutics

Since the end of the 1980s, key discoveries have been made which have significantly revived the scientific interest in a cell organelle, which has been studied continuously and with steady success for the last 100 years. It has become increasingly evident that mitochondrial dysfunction contributes to a variety of human disorders, ranging from neurodegenerative and neuromuscular diseases, obesity, and diabetes to ischemia-reperfusion injury and cancer. Moreover, since the middle of the 1990s, mitochondria, the 'power house' of the cell, have also become accepted as the cell's 'arsenals' reflecting their increasingly acknowledged key role during apoptosis. Based on these recent developments in mitochondrial research, increased pharmacological and pharmaceutical efforts have lead to the emergence of 'Mitochondrial Medicine' as a whole new field of biomedical research. Targeting of biologically active molecules to mitochondria in living cells will open up avenues for manipulating mitochondrial functions, which may result in the selective protection, repair or eradication of cells. This review gives a brief synopsis over current strategies of mitochondrial targeting and their possible therapeutic applications.

DQAsome-mediated delivery of plasmid DNA toward mitochondria in living cells

DQAsomes are mitochondriotropic cationic 'bola-lipid'-based vesicles, which have been developed by us for the transport of drugs and DNA to mitochondria in living cells. This has made direct mitochondrial gene therapy feasible for the very first time. Our strategy for the delivery of DNA into the matrix of mitochondria is based upon the DQAsomal transport of a DNA-signal peptide conjugate to mitochondria, the selective liberation of this conjugate from DQAsomes at the mitochondrial membrane followed by DNA uptake via the mitochondrial protein import machinery. Using membrane-mimicking liposomes and isolated rat liver mitochondria we have shown earlier that DQAsome-DNA complexes (DQAplexes) selectively release pDNA when in contact with mitochondria-like membranes. Employing a newly developed protocol for selectively staining free pDNA in the cytosol of living cells and based on confocal fluorescence microscopic imaging we demonstrate here that DQAplexes appear to be able to escape from endosomes without loosing their pDNA load and transport the pDNA to the site of mitochondria at which at least a portion of the pDNA is released from its DQAsomal carrier. Free pDNA could not be detected anywhere else inside the cytosol of transfected cells demonstrating the target-selectivity of DQAsome-mediated DNA delivery to mitochondria.

Optimizing the delivery systems of chimeric RNA.DNA oligonucleotides

Special oligonucleotides for targeted gene correction have attracted increasing attention recently, one of which is the chimeric RNA.DNA oligonucleotide (RDO) system. RDOs for targeted gene correction were first designed in 1996, and are typically 68 nucleotides in length including continuous RNA and DNA sequences (RNA is 2'-O-methyl-modified). They have a 25 bp double stranded region homologous to the targeted gene, two hairpin ends of T loop and a 5 bp GC clamp, that give the molecule much greater stability [Fig. 1]. One mismatch site in the middle of the double-stranded region is designed for targeted gene therapy. RDOs have been used recently for targeted gene correction of point mutations both in vitro and in vivo, but many problems must be solved before clinical application. One of the solutions is to optimize the delivery vectors for RDOs. To date, few RDO delivery systems have been used. Therefore, new vectors should be tried for RDO transfer, such as the use of nanoparticles. Additionally, different kinds of modifications should be applied to RDO carrier systems to increase the total correction efficiency in vivo. Only with the development of delivery systems can RDOs be used for gene therapy, and successfully applied to functional genomics.

Isothermic titration calorimetry to study CMCs of neutral surfactants and of the liposome-forming bolaamphiphile dequalinium

Isothermic titration calorimetry was used to measure the heat of micelle formation (molar enthalpy of transfer of surfactants monomers from water into micellar aggregates. The problems associated with the estimation of the CMC and the whole therodynamic profile of micellization of surfactants via Gibbs-Helmholtz-Equation are discussed. CMC's of octylthioglucoside and the peculiar bolaamphilphile dequalinium which concentrates in mitochondria are measured. In contrast to earlier reports, no CMC of dequalinium could be found inspite of extensive systematic measurements.

DQAsome/DNA complexes release DNA upon contact with isolated mouse liver mitochondria

DQAsomes are mitochondriotropic cationic vesicles, which have been developed by us for the supposed transport of DNA to mitochondria in living cells [Pharm. Res. 15 (1998) 334]. Our strategy for the delivery of DNA into the matrix of mitochondria is based upon the putative transport of a DNA-signal peptide conjugate to mitochondria, the liberation of this conjugate from DQAsomes at the mitochondrial membrane followed by DNA uptake via the mitochondrial protein import machinery. As a first and important step towards delivery of DNA into mitochondria of living cells, we studied the DNA release from DQAsomes upon contact with non-energized mitochondria in vitro. Mitochondria were isolated from mouse liver and characterized by electron microscopy and the determination of mitochondrial marker enzyme activity. DQAsomes were added to DNA in the presence of SYBR Green I resulting in the formation of DQAsome/DNA complex and the complete loss of fluorescence. Following the addition of isolated mitochondria to DQAsome/DNA complex, the fluorescence signal was recovered due to the dissociation of DNA from its cationic carrier. Thus, DQAsome/DNA complexes were shown to release DNA upon contact with the surface of mitochondria thereby meeting a key requirement for our strategy towards mitochondrial DNA delivery.

Targeting large molecules to mitochondria

Mitochondrial function is central to a range of cell processes and mitochondrial dysfunction contributes to a number of human diseases. Consequently there is growing interest in delivering large molecules such as nucleic acids, proteins, enzyme mimetics, drugs and probes to mitochondria within cells. The reasons for doing this are to understand how mitochondria function in the cell and to develop therapies for diseases involving mitochondrial damage. Here we review the methods that have been used to target large molecules to mitochondria and discuss some approaches under development.