Current Drug Metabolism (v.14, #3)

Stem cells may be applied to improve the efficiency of drug discovery, but more effective protocols are first required to control the differentiation. Recent researches have revealed that physical stimulation is an important avenue for stem cell lineage commitment, such as electrical field stimulation. Here, we review literatures about stem cell differentiation by electrical field stimulation. Various forms of electrical fields with soluble induction factors have shown to produce a synergistic effect in order to enhance the osteogenic commitment. Moreover, electrical field stimulation alone shows marked effects of pre-commitment to cardiomyocyte and neuron. However, the related precise molecular regulatory mechanism is unclear. As cardiomyocyte and neuron are crucial factors in drug development process, electrical field stimulation may be proposed as an effect important for stem cell differentiation, exhibiting a potential application in drug discovery.

In Vivo DNA Electrotransfer for Immunotherapy of Cancer and Neurodegenerative Diseases by Daniela Fioretti, Sandra Iurescia, Vito Michele Fazio, Monica Rinaldi (279-290).
Electroporation is the process commonly referred to the transient increase in the permeability of cell membranes on submission to electric field pulses. Electroporation has become an increasingly extensive method to enhance in vivo DNA delivery for both gene therapy applications as well as for delivery of DNA vaccines, mostly against cancer. In vivo gene electrotransfer is of special interest since it is the most efficient non-viral strategy for gene delivery and it is worthy of low manufacturing costs, ease of realization and favorable safety profile. No adverse findings observed in toxicology and biodistribution/integration studies have been warranted for the evaluation of this approach in humans. Therefore, gene delivery followed by electroporation is currently being investigated in several clinical trials. The positive outcomes of early studies suggest that the efficacy of gene delivery and immunogenicity has greatly improved by electroporation. This review briefly summarizes salient features and recent findings that have contributed to the rapid progress of electroimmunotherapy as well as an overview of advanced clinical studies in oncology. Translation of in vivo DNA electrovaccination for neurodegenerative diseases as well as future expectations are also discussed.

Electroporation in DNA Vaccination Protocols Against Cancer by Pieranna Chiarella, Vito Michele Fazio, Emanuela Signori (291-299).
Since conventional therapeutic approaches in cancer are highly invasive they hardly prolong patient survival for more than few months. Having the ability to stimulate both cellular and humoural immune responses, immunisation with naked plasmid DNA encoding tumour-associated antigens or tumour-specific antigens has recently reported a plethora of advantages, and the improvement of vaccine efficacy has emerged as a goal in the development of DNA vaccination as anti-tumour therapy. Nevertheless, because of their poor immunogenicity when administered as unformulated intramuscular injections, plasmid DNA vaccines need to be improved. Recent data suggest that the DNA vaccine efficacy may significantly be increased by electroporation. This review highlights the recent literature that supports electroporation as an effective strategy to improve DNA-based vaccination protocols, investigating the most relevant studies, recently developed for the applications of DNA vaccine electrotransfer against tumours in pre-clinical and clinical studies.

Nucleic Acids Electro-transfer: From Bench to Bedside by Sophie Chabot, Christelle Rosazza, Muriel Golzio, Andreas Zumbusch, Justin Teissie, Marie-Pierre Rols (300-308).
There are a number of stigmas attached to the development of antitumor drugs such as their safe and efficient delivery into target cells or tissues. The one such case is that of macromolecules, such as nucleic acids where it poses severe limits. From this point of view, electro-pulsation proves to be a promising method for cancer-associated gene therapy. It involves the direct application of electric pulses on cells or tissues which leads to a transient permeabilization of their plasma membrane allowing efficient in vitro and in vivo delivery of exogenous molecules. The present review probes the electrotransfer of nucleic acids, the nature of nucleic acids (plasmid DNA, mRNA, siRNA, LNA...) which can be electrotransferred and the mechanism of their electrotransfer.

Advances in Photodynamic Therapy Assisted by Electroporation by Malgorzata Kotulska, Julita Kulbacka, Jolanta Saczko (309-318).
Low invasive therapies of cancer are directed toward the methods that target selectively on carcinoma cells. Photodynamic therapy (PDT) is a therapeutic modality in which combination of a photosensitizer, light, and oxygen renders reactive oxygen species (ROS) which cause damage to a tumor tissue. Each of these factors is not toxic in itself and the effect of therapy results from high uptake of a photosensitizer by carcinoma cells and directed tumor irradiation by light. Realization of the therapy depends on efficient transport of the photosensitizer across the membrane and intracellular accumulation of the drug. Depending on the treatment conditions and the uptake mechanism, sensitizers can potentially reach different intracellular concentrations and different cellular effects can be triggered. Transport efficacy can be significantly augmented by applying electric pulses to plasma membrane, which opens transient non-selective hydrophilic nanopores as additional pathways across lipid membranes. Electroporation (EP) has been utilized to facilitate drug uptake in electrochemotherapy (ECT) and has been tested in combination with PDT. In the review, we described effects of PDT and electrophotodynamic therapy (EPDT) on carcinoma and healthy cells, studied in vitro and vivo. The comparison of different drugs has been applied to tests considering the enhancement of their cytotoxicity, selectivity, and additional effects caused by electroporation.

Gene Transfer and Drug Delivery with Electric Pulse Generators by Chenguo Yao, Fei Guo, Chengxiang Li, Caixin Sun (319-323).
Electroporation is a process that involves a series of intense electric pulses used to overcome the barrier of the cell membrane. The application of an external electric field may result in reversible breakdown of cell membrane. This transient state helps to introduce cells with a variety of different molecules, such as DNA and drug molecules, and is known as the fundamental mechanisms of gene transfer and drug delivery with electric pulses. This paper reviews (1) the utility of electric pulse generators in gene transfer and drug delivery, (2) development of electric pulse generators for utilizing them in gene transfer and drug delivery, (3) study of parameters of electric pulses used in gene transfer and drug delivery, (4) study of electrode configurations used in gene transfer and drug delivery.

Insight into Tissue Unbound Concentration: Utility in Drug Discovery and Development by T. Thanga Mariappan, Sandhya Mandlekar, Punit Marathe (324-340).
In a preclinical setting, plasma or whole tissue drug concentrations are often correlated with pharmacodynamics, although according to the free drug hypothesis, unbound drug concentration should be more pharmacologically relevant. Alternatively, blood concentrations may be a good surrogate for tissue concentration for passively permeable compounds. However, for a large number of compounds that are substrates for uptake and/or efflux transporters expressed at the tissue level, significant discrepancies are expected between unbound concentrations in blood and those in tissues. Consequently, attempts have been made to measure tissue unbound drug concentrations using tissue homogenates, slices and microdialysis. Mathematical expressions for calculating the rate and extent of drug distribution into tissues have also been established. For example, a ratio of unbound concentration in the tissue to that in plasma (Kp,uu) is the best indicator of the extent of tissue distribution. Despite these technical advances, however, very few examples demonstrate a focus on tissue unbound drug concentrations in a preclinical setting. This review will illustrate various techniques to estimate tissue unbound drug concentrations, relevant parameters to calculate the rate and extent of tissue distribution and different factors affecting tissue unbound concentration. The review will also highlight various examples from the literature where tissue unbound drug concentrations have demonstrated a superior correlation with efficacy. The impact of tissue unbound drug concentrations on the projection of human efficacious dose is also discussed.

Pregnane X Receptor (PXR) at the Crossroads of Human Metabolism and Disease by Ioannis Koutsounas, Stamatios Theocharis, Efstratios Patsouris, Constantinos Giaginis (341-350).
Pregnane X Receptor (PXR), a member of the nuclear receptor (NR) superfamily, is expressed in liver and intestine, as also in other tissues and cells. PXR is activated by a wide variety of endobiotics, dietary compounds and pharmaceuticals. This nuclear receptor serves as a master transcriptional regulator of CYP3A isozymes, and also regulates a large number of enzymes and transporters involved in the pharmacokinetics of both endobiotics and xenobiotics. PXR has an impact on energy homeostasis through glucose and lipid metabolism regulation. PXR activation is also hepatoprotective against toxic bile acids. New roles for PXR have been identified in bone homeostasis, inflammatory bowel disease, liver steatosis and fibrogenesis. PXR directly regulates the expression of multidrug resistance protein 1 (MDR1) and other important proteins involved in drug metabolism. Drug-drug interactions can affect patients with cardiovascular disease, tuberculosis, HIV and cancer. Especially cancer patients are at high risk of such interactions, as treated with multi-drug combinations. PXR activation can affect the efficacy of chemotherapeutics, thus targeting PXR may represent a novel strategy for the improvement of the pharmacokinetics of chemotherapeutic agents, thereby providing safer and more effective therapies for cancer patients.

A Review on Noscapine, and its Impact on Heme Metabolism by Harpal Singh, Prashant Singh, Kamlesh Kumari, Ankush Chandra, Sujata K. Dass, Ramesh Chandra (351-360).
This review introduces the Noscapine, which is being used as an antitussive drug for a long time has been recently discovered as a novel tubulin–binding, anti-angiogenic anticancer drug that causes cell cycle arrest and induces apoptosis in cancer cells both in vitro as well as in vivo. Noscapine is a multifunctional molecule i.e. it possesses various functional moieties. We maneuvered various amenable sites and have synthesized analogs, which might prove to be more efficacious and less cytotoxic. Moreover, development of oral controlled release anticancer formulation of noscapine is severely hampered due to short biological half-life ( < 2-h), poor absorption, low aqueous solubility, and extensive first pass metabolism, thereby requiring large doses for effective treatment.

Xenobiotic Sulphation and its Variability During Inflammation: a Factor in Adverse Drug Reactions? by R.H. Waring, R.M. Harris, J.O. Hunter, S.C. Mitchell (361-365).
The interactions between disease processes and the metabolism of therapeutic drugs have not been systematically investigated. Inflammation, with the presence of pro-inflammatory cytokines, affects Phase 1 metabolism, particularly the activity of the CYP isoforms. Inflammatory factors also alter the activity of some Phase 2 enzymes, particularly the sulphotransferases (SULT isoforms) responsible for drug sulphonation and the enzyme pathway involved in the supply of sulphate for this reaction. Being ill may, therefore, in itself make drug metabolism unpredictable.