Antibacterial and transfection activities of nebulized formulations incorporating long n-alkyl chain silver N-heterocyclic carbene complexes.

The development of new antibacterial molecules is essential in view of the emergence of pathogenic strains resistant to multiple antibiotics. Among the infectious pathologies, pulmonary infections are particularly difficult to treat due to the complexity of lung anatomy and the presence of natural barriers such as mucus. At present, the aerosol delivery of antibacterial compounds is still poorly employed. Furthermore, the presence of bacteria in lungs negatively affects aerosolized Cystic Fibrosis gene therapy efficiency. A multi-functional formulation (antibacterial and transfection activities) could increase the therapeutic effect. This work reports the synthesis of new N-heterocyclic carbene silver complexes (Ag-NHC) featuring a lipid chain and the evaluation of their antibacterial potency, especially when delivered following aerosolization. When formulated alone in water, these Ag-NHC displayed remarkable antibacterial activities against some Staphyloccocus aureus strains and Pseudomonas aeruginosa clinical strains. Moreover, combined with cationic lipid and DNA (ternary combination), they could be used to deliver therapeutic genes via aerosolization in infected lungs. Altogether, the data reported herein support n-alkyl chain Ag-NHC as a possible alternative to conventional antibiotics for treating respiratory infections and to combat the emergence of multi-resistant bacteria.

Antibacterial effect and DNA delivery using a combination of an arsonium-containing lipophosphoramide with an N-heterocyclic carbene-silver complex - Potential benefits for cystic fibrosis lung gene therapy.

Cystic Fibrosis (CF), the most common chronic genetic disorder among the Caucasian population, is a life-threatening disease mainly due to respiratory failures resulting from chronic infections and inflammation. Although research in the pharmacological field has recently made significant progress, gene therapy still remains a promising strategy to cure CF, especially because it should be applicable to any patient whatever the mutation profile. Until now, little attention has been paid to bacterial lung infections with regard to gene delivery to the airways; yet, this could greatly impact on the success of gene therapy. Previously, we have reported arsonium-containing lipophosphoramides as poly-functional nanocarriers capable of simultaneous antibacterial action against Gram-positive bacteria and gene transfer into eukaryotic cells. In the present work, we show that such nanoparticles can also be combined with an N-heterocyclic carbene-silver complex in order to extend the spectrum of antibacterial activity, including towards the Gram-negative Pseudomonas aeruginosa. Importantly, this is demonstrated not only using standard in vitro protocols but also a clinically-relevant aerosol delivery method. Furthermore, antibacterial effects are compatible with efficient and safe gene delivery into human bronchial epithelial cells. The poly-functionality of combinations of such chemical compounds may thus show benefits for CF lung gene therapy.

Enhancement of lung gene delivery after aerosol: a new strategy using non-viral complexes with antibacterial properties.

The pathophysiology of obstructive pulmonary diseases, such as cystic fibrosis (CF), leads to the development of chronic infections in the respiratory tract. Thus, the symptomatic management of the disease requires, in particular, repetitive antibiotherapy. Besides these antibacterial treatments, certain pathologies, such as CF or chronic obstructive pulmonary disease (COPD), require the intake of many drugs. This simultaneous absorption may lead to undesirable drug interactions. For example, Orkambi® (lumacaftor/Ivacaftor, Vertex), a pharmacological drug employed to treat F508del patients, cannot be used with antibiotics such as rifampicin or rifabutin (rifamycin family) which are necessary to treat Mycobacteriaceae. As far as gene therapy is concerned, bacteria and/or biofilm in the airways present an additional barrier for gene transfer. Thus, aerosol administration of nanoparticles have to overcome many obstacles before allowing cellular penetration of therapeutic compounds. This review focusses on the development of aerosol formulations adapted to the respiratory tract and its multiple barriers. Then, formulations that are currently used in clinical applications are summarized depending on the active molecule delivered. Finally, we focus on new therapeutic approaches to reduce possible drug interactions by transferring the antibacterial activity to the nanocarrier while ensuring the transfection efficiency.

Efficient ferrocifen anticancer drug and Bcl-2 gene therapy using lipid nanocapsules on human melanoma xenograft in mouse.

Metastatic melanoma has been described as a highly aggressive cancer with low sensibility to chemotherapeutic agents. New types of drug, such as metal-based drugs (ferrocifens) have emerged and could represent an alternative for melanoma treatment since they show interesting anticancer potential. Furthermore, molecular analysis has evidenced the role of apoptosis in the low sensibility of melanomas and especially of the key regulator, Bcl-2. The objective of this study was to combine two strategies in the same lipid nanocapsules (LNCs): i) gene therapy to modulate anti-apoptotic proteins by the use of Bcl-2 siRNA, and ii) ferrocifens as a new type of anticancer agent. The efficient gene silencing with LNCs was verified by the specific extinction of Bcl-2 in melanoma cells. The cellular toxicity of ferrocifens (ferrociphenol (FcDiOH) or Ansa-FcDiOH) was demonstrated, showing higher efficacy than dacarbazine. Interestingly, the association of siBcl-2 LNCs with Ansa-FcDiOH demonstrated a significant effect on melanoma cell viability. Moreover, the co-encapsulation of siRNA and ferrocifens was successfully performed into LNCs for animal experiments. A reduction of tumor volume and mass was proved after siBcl-2 LNC treatment and Ansa-FcDiOH LNC treatment, individually (around 25%). Finally, the association of both components into the same LNCs increased the reduction of tumor volume to about 50% compared to the control group. In conclusion, LNCs appeared to provide a promising tool for the co-encapsulation of a metal-based drug and siRNA.

Evaluation of New Fluorescent Lipophosphoramidates for Gene Transfer and Biodistribution Studies after Systemic Administration.

The objective of lung gene therapy is to reach the respiratory epithelial cells in order to deliver a functional nucleic acid sequence. To improve the synthetic carrier's efficacy, knowledge of their biodistribution and elimination pathways, as well as cellular barriers faced, depending on the administration route, is necessary. Indeed, the in vivo fate guides the adaptation of their chemical structure and formulation to increase their transfection capacity while maintaining their tolerance. With this goal, lipidic fluorescent probes were synthesized and formulated with cationic lipophosphoramidate KLN47 (KLN: Karine Le Ny). We found that such formulations present constant compaction properties and similar transfection results without inducing additional cytotoxicity. Next, biodistribution profiles of pegylated and unpegylated lipoplexes were compared after systemic injection in mice. Pegylation of complexes led to a prolonged circulation in the bloodstream, whereas their in vivo bioluminescent expression profiles were similar. Moreover, systemic administration of pegylated lipoplexes resulted in a transient liver toxicity. These results indicate that these new fluorescent compounds could be added into lipoplexes in small amounts without perturbing the transfection capacities of the formulations. Such additional properties allow exploration of the in vivo biodistribution profiles of synthetic carriers as well as the expression intensity of the reporter gene.

Prevalidation of the rat CFU-GM assay for in vitro toxicology applications.

In vitro haematotoxicity assays are thought to have the potential to significantly reduce and refine the use of animals for haematotoxicity testing. These assays are used successfully in all types of studies - however, their use is not so common in human toxicology studies in the preclinical setting, as they are not required for regulatory testing in this case. Furthermore, these assays could play a key role in bridging the gap between preclinical toxicology studies in animal models and clinical investigations. In previous studies, the Colony Forming Unit-Granulocyte Macrophage (CFU-GM) assay has been validated for testing drug haematotoxicity (with both mouse bone-marrow and human cord blood) and for predicting the in vivo human maximal tolerated dose (MTD) by adjusting in vivo data on mouse toxicity. Recently, a Colony Forming Unit-Megakaryocyte (CFU-MK) assay has also been prevalidated for testing drug toxicity toward megakaryocytes. The rat CFU-GM assay has been used by many researchers for its ability to evaluate in vitro haematotoxicity. Although it is not yet available, a standardised procedure for data comparison could be very important, since the rat is the most widely-used species for the in vivo testing of toxicants. This report presents the results of the prevalidation study developed to analyse the intra-laboratory and inter-laboratory variability of a standardised operating procedure for this assay and its performance for the in vitro determination of the inhibitory concentration (IC) values of drugs on rat myeloid progenitors (CFU-GM). The results demonstrate that the CFU-GM assay can be performed with cryopreserved rat bone-marrow cells (rBMC). The assay represents a useful tool for evaluating the toxicity of a compound, in terms of both relative toxicity (when different molecules are compared) and the prediction of the degree of in vivo toxicity. The use of this assay could greatly reduce the number of rats used in experimental procedures, and could also contribute to the accumulation of more toxicity data on compounds to be registered according to the criteria established by the European Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) programme.

Synthesis and antitumor activity of novel dibutyltin carboxylates of aminoglucosyl derivatives.

In this study, di-n-butyltin(IV) oxide was reacted with the amino glucose analog, cis-4-[N-(1',3',4',6'-tetra-O-benzoyl-2-deoxy-glucopyranosyl)imido]-4-oxo-2-butenoic acid (1a) and o-[N-(1',3',4',6'-tetra-O-benzoyl-2-deoxy-glucopyranosyl) carbamoyl] benzoic acid (2a) to give the complexes bis-{cis-4-[N-(1',3',4',6'-tetra-O-benzoyl-2-deoxy-glucopyranosyl)imido-4-oxo-2-butenoic acid]-di-n-butyltin} carboxylate (1) and bis-{o-[N-(1',3',4',6'-tetra-O-benzoyl-2-deoxy-glucopyranosyl) carbamoyl-benzoic acid]-di-n-butyltin}carboxylate (2). These two compounds were then characterized by IR, NMR and MS. In vitro tests showed that both compounds have high cytotoxicity in four tumor cell lines (P388, HL-60, A549 and BEL-7402). Clonogenic assays demonstrated that both compounds 1 and 2 have hematopoietic cell toxicity at 10(-6) M.

CFU-MK assay for acute thrombocytopenia.

In this unit, protocols to culture human platelet progenitors (Colony Forming Unit-Megakaryocyte; CFU-M) with or without toxicants are described. Platelet progenitors are obtained from human umbilical cord blood. After separation of mononuclear cells, the cell suspension can be cryopreserved or plated immediately. Megakaryocytes are identified by immunocytochemistry. Test chemicals are added to the culture medium before cells are plated. Megakaryocytes are scored after 12 days of culture. IC(10), IC(50) and IC(90) can be calculated by comparison to control cultures. A predictive model is proposed to evaluate the hazard of thrombocytopenia induced by chemicals. When IC(50) and IC(90) are below C(max) in humans, the likelihood of thrombocytopenia is strong.