Régis Vanderesse

Characterization of α -casozepine, a tryptic peptide from bovine α s1-casein with benzodiazepine-like activity

Caseins are a known source of biologically active peptides. In this study, we have shown evidence of a novel anxiolytic activity in a tryptic hydrolysate of bovine αs1‐casein. Injection of 3 mg/kg of this hydrolysate significantly reduced the epileptic symptoms caused by pentylenetetrazole in rats. Anxiety reduction was also observed when the hydrolysate was tested in the elevated plus‐maze and in the conditioned defensive burying rat models. Peptides isolated from the hydrolysate were examined for their affinity for the γ‐amino‐butyric acid (GABA) type A receptor. Only one peptide, named α‐casozepine, corresponding to the 91–100 fragment from bovine αs1‐casein, expressed affinity for GABAA receptor. In vitro, the peptide had 10,000 less affinity for the benzodiazepine site of the GABAA than did diazepam. However, in the conditioned defensive burying paradigm it was 10‐fold more efficient than diazepam. The difference observed between the in vitro and in vivo activity of α‐casozepine could not been explained by an action via the peripheral‐type benzodiazepine receptor; α‐casozepine had no affinity for this receptor. The α‐casozepine amino acid sequence could be related to the carboxy‐terminal sequence of the polypeptide diazepam binding inhibitor, an endogenous ligand of the central GABAA and peripheral‐type benzodiazepine receptors.

Non polymeric nanoparticles for photodynamic therapy applications: recent developments.

Photodynamic therapy has emerged as an alternative to chemotherapy and radiotherapy for cancer treatment. Nanoparticles have recently been proposed as effective carriers for photosensitizers. Depending on their chemical composition, these can be used for diagnosis and therapy due to the selective accumulation of the photosensitizer in cancer cells in vitro or in tumors in vivo. Multifunctional nanoplatforms combining several applications within the same nano-object emerge as potential important theranostic tools. This review, based on the chemical nature of the nanoparticles will discuss recent advances in the area of non polymeric nanoparticles for photodynamic therapy applications.

Recent Improvements in the Use of Synthetic Peptides for a Selective Photodynamic Therapy

Photodynamic therapy (PDT) is a relatively new cytotoxic treatment, predominantly used in anti-cancer approaches, that depends on the retention of photosensitizers in tumor and their activation after light exposure. Photosensitizers are photoactive compounds such as porphyrins and chlorins that upon photoactivation, effect strongly localized oxidative damage within the target cells. The ability to confine activation of the photosensitizer by restricting illumination to the tumor allows for a certain degree of selectivity. Nevertheless, the targeted delivery of photosensitizers to defined cells is a major problem in PDT of cancer, and one area of importance is photosensitizer targeting. Alterations or increased levels in receptor expression of specific cellular type occur in the diseased tissues. Therefore, photosensitizers can be covalently attached to molecules such as peptides, leading to a receptor-mediated targeting strategy. These active-targeting approaches may be particularly useful for anti-vascular PDT. Moreover, it has been shown that the photocytotoxicity of photodynamic drugs could be enhanced by delivering high amounts of a photosensitizer into subcellular organelles such as the nucleus where nucleic acids represent target molecules sensitive to photodamage. The recent progresses in the use of active-targeting strategy with synthetic peptides and the interest of using an active-targeting strategy in PDT, which could allow efficient cellular internalization of photosensitizers, are described in this review.

Multifunctional Peptide-Conjugated Hybrid Silica Nanoparticles for Photodynamic Therapy and MRI

Photodynamic therapy (PDT) is an emerging theranostic modality for various cancer as well as non-cancer diseases. Its efficiency is mainly based on a selective accumulation of PDT and imaging agents in tumor tissue. The vascular effect is widely accepted to play a major role in tumor eradication by PDT. To promote this vascular effect, we previously demonstrated the interest of using an active- targeting strategy targeting neuropilin-1 (NRP-1), mainly over-expressed by tumor angiogenic vessels. For an integrated vascular-targeted PDT with magnetic resonance imaging (MRI) of cancer, we developed multifunctional gadolinium-based nanoparticles consisting of a surface-localized tumor vasculature targeting NRP-1 peptide and polysiloxane nanoparticles with gadolinium chelated by DOTA derivatives on the surface and a chlorin as photosensitizer. The nanoparticles were surface-functionalized with hydrophilic DOTA chelates and also used as a scaffold for the targeting peptide grafting. In vitro investigations demonstrated the ability of multifunctional nanoparticles to preserve the photophysical properties of the encapsulated photosensitizer and to confer photosensitivity to MDA-MB-231 cancer cells related to photosensitizer concentration and light dose. Using binding test, we revealed the ability of peptide-functionalized nanoparticles to target NRP-1 recombinant protein. Importantly, after intravenous injection of the multifunctional nanoparticles in rats bearing intracranial U87 glioblastoma, a positive MRI contrast enhancement was specifically observed in tumor tissue. Real-time MRI analysis revealed the ability of the targeting peptide to confer specific intratumoral retention of the multifunctional nanoparticles.

Activation of reducing agents. Sodium hydride containing complex reducing agents 23. Symmetrical coupling of nitrogen-containing heterocyclic halides

Abstract The preparation of NiCRA (NaH-B u t ONa-Ni(OAc) 2 ) in the presence of PPh 3 , leads to a reagent (termed NiCRA-PPh 3 ) which is shown to be one of the most efficient Ni containing reagents reported so far for the homocoupling of heteroaromatic halides.

Folding Types of Dipeptides Containing the Diastereoisomeric Cyclopropanic Analogues of Phenylalanine

Abstract In order to consider the possible influence of the orientation of a side chain on the peptide backbone, we have studied the molecular structure of four t BuCO-Pro-c 3 Phe-NHMe model dipeptides, where c 3 Phe denotes each of the four diastereoisomeric 2,3-methanophenylalanines, by using IR and proton NMR experiments. All four derivatives are β-folded, but the folding type depends on the stereochemistry of the cyclopropane moiety.

Activation of reducing agents: sodium hydride containing complex reducing agents. XIX: Homo coupling of aryl and vinyl halides promoted by ligand modified NiCRA (NaH-RONa-Ni(OAc)2)

Abstract The preparation of NiCRA (NaH-t-AmONa-Ni(OAc) 2 ) in the presence of 2,2′-bipyridine (bpy) leads to a new reagent (termed NiCRA-bpy) which is shown to be one of the most efficient Ni based reagents reported so far for the homocoupling of aryl and vinyl halides (including chlorides). The homo coupling of cis - and trans -β-bromostyrenes is shown to be stereospecific.

Inorganic Nanoparticles for Photodynamic Therapy.

Photodynamic therapy (PDT) is a well-established technique employed to treat aged macular degeneration and certain types of cancer, or to kill microbes by using a photoactivatable molecule (a photosensitizer, PS) combined with light of an appropriate wavelength and oxygen. Many PSs are used against cancer but none of them are highly specific. Moreover, most are hydrophobic, so are poorly soluble in aqueous media. To improve both the transportation of the compounds and the selectivity of the treatment, nanoparticles (NPs) have been designed. Thanks to their small size, these can accumulate in a tumor because of the well-known enhanced permeability effect. By changing the composition of the nanoparticles it is also possible to achieve other goals, such as (1) targeting receptors that are over-expressed on tumoral cells or neovessels, (2) making them able to absorb two photons (upconversion or biphoton), and (3) improving singlet oxygen generation by the surface plasmon resonance effect (gold nanoparticles). In this chapter we describe recent developments with inorganic NPs in the PDT domain. Pertinent examples selected from the literature are used to illustrate advances in the field. We do not consider either polymeric nanoparticles or quantum dots, as these are developed in other chapters.

Functionalized silica-based nanoparticles for photodynamic therapy

AIM The strategy developed aims to favor the vascular effect of photodynamic therapy by targeting tumor-associated vascularization using peptide-functionalized nanoparticles. We previously described the conjugation of a photosensitizer to a peptide targeting neuropilin-1 overexpressed in tumor angiogenic vessels. MATERIALS & METHODS In this study, we have designed and photophysically characterized a multifunctional nanoparticle consisting of a surface-localized tumor vasculature targeting peptides and encapsulated photodynamic therapy and imaging agents. RESULTS & CONCLUSION The elaboration of these multifunctional silica-based nanoparticles is reported. Nanoparticles functionalized with approximately 4.2 peptides bound to recombinant neuropilin-1 protein. Nanoparticles conferred photosensitivity to cells overexpressing neuropilin-1, providing evidence that the chlorin grafted within the nanoparticle matrix can be photoactivated to yield photocytotoxic effects in vitro.

Photodynamic therapy targeting neuropilin-1: Interest of pseudopeptides with improved stability properties.

The general strategy developed aims to favor the vascular effect of photodynamic therapy by targeting tumor vasculature. Since angiogenic endothelial cells represent an interesting target to potentiate this vascular effect, we previously described the conjugation of a photosensitizer to a peptide targeting neuropilins (NRPs) over-expressed specially in tumor angiogenic vessels and we recently characterized the mechanism of photosensitization-induced thrombogenic events. Nevertheless, in glioma-bearing nude mice, we demonstrated that the peptide moiety was degraded to various rates according to time after intravenous administration. In this study, new peptidases-resistant pseudopeptides were tested, demonstrating a molecular affinity for NRP-1 and NRP-2 recombinant chimeric proteins and devoid of affinity for VEGF receptor type 1 (Flt-1). To argue the involvement of NRP-1, MDA-MB-231 breast cancer cells were used, strongly over-expressing NRP-1 receptor. We evidenced a statistically significant decrease of the different peptides-conjugated photosensitizers uptake after RNA interference-mediated silencing of NRP-1. Peptides-conjugated photosensitizers allowed a selective accumulation into cells. In mice, no degradation was observed in plasma in vivo 4h after intravenous injection by MALDI-TOF mass spectrometry. This study draws attention to this potential problem with peptides, especially in the case of targeting strategies, and provides useful information for the future design of more stable molecules.