Search

Cannabis has been used for decades as a palliative therapy in the treatment of cancer. This is because of its beneficial effects on the pain and nausea that patients can experience as a result of chemo/radiotherapy. Tetrahydrocannabinol and cannabidiol are the main compounds present in Cannabis sativa, and both exert their actions through a receptor-mediated mechanism and through a non-receptor-mediated mechanism, which modulates the formation of reactive oxygen species. These oxidative stress conditions might trigger lipidic changes, which would compromise cell membrane stability and viability. In this sense, numerous pieces of evidence describe a potential antitumor effect of cannabinoid compounds in different types of cancer, although controversial results limit their implementation. In order to further investigate the possible mechanism involved in the antitumoral effects of cannabinoids, three extracts isolated from Cannabis sativa strains with high cannabidiol content were analyzed. Cell mortality, cytochrome c oxidase activity and the lipid composition of SH-SY5Y cells were determined in the absence and presence of specific cannabinoid ligands, with and without antioxidant pre-treatment. The cell mortality induced by the extracts in this study appeared to be related to the inhibition of the cytochrome c oxidase activity and to the THC concentration. This effect on cell viability was similar to that observed with the cannabinoid agonist WIN55,212-2. The effect was partially blocked by the selective CB1 antagonist AM281, and the antioxidant α-tocopherol. Moreover, certain membrane lipids were affected by the extracts, which demonstrated the importance of oxidative stress in the potential antitumoral effects of cannabinoids. This work has been partially supported by a grant from the Ministry of Economy and Competitiveness (DIN2019-010902 and DIN2020-011349) and the Basque Government Department of Economic Development, Sustainability and Environment (Bikaintek program: 005-B2/2021).

The production of reactive oxygen species (ROS) increases considerably in situations of cellular stress, inducing lipid peroxidation and multiple alterations in proteins and nucleic acids. However, sensitivity to oxidative damage varies between organs and tissues depending on the triggering process. Certain drugs used in the treatment of diverse diseases such as malaria have side effects similar to those produced by oxidative damage, although no specific study has been conducted. For this purpose, cell membrane microarrays were developed and the superoxide production evoked by the mitochondrial activity was assayed in the presence of specific inhibitors: rotenone, antimycin A and azide. Once the protocol was set up on cell membrane isolated from rat brain areas, the effect of six antimalarial drugs (atovaquone, quinidine, doxycycline, mefloquine, artemisinin, and tafenoquine) and two essential oils (Rosmarinus officinalis and Origanum majoricum) were evaluated in multiple human samples. The basal activity was different depending on the type of tissue, the liver, jejunum and adrenal gland being the ones with the highest amount of superoxide. The antimalarial drugs studied showed specific behavior according to the type of human tissue analyzed, with atovaquone and quinidine producing the highest percentage of superoxide formation, and doxycycline the lowest. In conclusion, the analysis of superoxide production evaluated in cell membranes of a collection of human tissues allowed for the characterization of the safety profile of these antimalarial drugs against toxicity mediated by oxidative stress This work has been partially supported by grant Ministry of Economy and Competitiveness PID2019-106222RB-C31/SRA (State Research Agency, 10.13039/501100011033), the Basque Government Department of Economic Development, Sustainability and Environment (PUE21-03 and Bikaintek program: 48-AF-W2-2019-7 and 007-B2/2020) and University of the Basque Country (price to the best Master Thesis in collaboration with Institutions and Business).

The αv β3 integrin receptor plays an important role in tumor metastasis and tumor-induced angiogenesis. The inhibition of this receptor with diverse ligands, antibodies, or cyclic peptides is a promising research field for the treatment of a variety of tumors. The replacement of Phe-(Me)Val dipeptide by a β-lactam ring in Cilengitide has led to new products that show higher inhibitory activity than the parent cyclopeptide. In particular, substitution of a peptide bond β-lactam-NH-Asp linkage by a β-lactam-O-Asp ester linkage increases the activity of the new cyclodepsipeptide. In the same way it has been found that open-chain compounds of the form Asp-β-lactam-Arg can interact with the receptor and inhibit its activity moderately. The integrin inhibitory activity of the synthesized compounds has been established by using the CGH array, a method that appears to be a more reliable trial than the classical adhesion test.

The α

Angiogenesis is a fundamental step in the transition of solid tumors from a dormant state to a malign one. Many of the low-molecular-weight anti-angiogenic drug candidates mimic the short peptide epitope Arg-Gly-Asp (RGD), disrupting the extracellular matrix/integrin adhesion and, ultimately, leading to tumor cell apoptosis. In contrast to the detailed structural information available for the extracellular adhesion inhibition of endothelial cells through the recognition of integrins (typically aVb3) by RGD peptidomimetics, [2] most aspects of possible intracellular angiogenic gene regulation caused by peptidomimetics remain unexplored. Importantly, dysfunction of this signaling system is suspected to be behind the resistance phenomena developed in anti-angiogenic therapies. Inside the endothelial cell, dozens of proteins mediate or control the signaling pathways of angiogenesis after integrin activation, but only a couple of kinases (JNK, ERK) and transcription factors (NFkB, FoxO) are able to promote gene regulation (Figure 1). In addition, large environmental ligands, such as vascular endothelial growth factors (VEGFs) or peptide hormones, are required to elicit proangiogenic gene regulation. In this context, we set out to design alternative lowmolecular-weight RGD probes for interaction with aVb3 integrin and gene regulation in HUVECs. Ideally, these peptidomimetics should: 1) contain a minimal scaffold to prevent undesired scaffold/integrin interactions, 2) have a uniform and predictable scaffold conformation, 3) bear a maximum of recognition groups, including hydrophobic or hydrophilic ones, and 4) permit the deletion of selected residues from the RGD triad without global shape change. We selected five-membered and four-membered small cyclic peptides for development. The residual flexibility of these cyclopeptides can be further constrained by incorporating lactam bridges between neighboring amino acids to stabilize protein secondary structure motifs characterized by combinations of b-turns and/or g-turns. Several lactam pseudopeptides resulting from such an extension of Freidinger’s concept (Scheme 1; 1!2) have been explored with the goals of mimicking receptor-bound conformations of bioactive peptides and of providing pharmacophore information for nonpeptide drug design. However, despite its apparent simplicity, this design is not always reliable for the precise positioning of a maximum number of recognition groups around the pseudopeptide cyclic core. Because the interresidual lactam bridge created by modification of the side chain (R) shares recognition and constraint functions, the design of mimetic libraries becomes difficult and non-general, when synthetically achievable. An alternative way to constrain cyclic peptides is based on the incorporation of a d-amino acid and an N-alkyl-amino acid into the macrocycle, as illustrated by the remarkable aVb3 antagonist cilengitide (3, cyclo-[Arg-Gly-Asp-d-Phe-N(Me)Val]) developed by Kessler et al. Here we report an alternative, more versatile solution to the above design problem, by introducing a-amino-b-lactam scaffolds originating from aCH/NH proton mimicry (Scheme 2; 1! 4). This “b-lactam scaffold-assisted design” (b-LSAD) approach is based on the separation of recognition and constraint groups, and has previously proven efficient for promotion of unusually stable type-II (II’) b-turn peptidomimetics from extended open native peptides. Accordingly, the straight application of the b-LSAD principle to RGD cyclic mimetics led us to the b-lactam pseudopeptides 4a–d, which fulfilled several structural requirements to trigger quite different signaling interactions with aVb3 integrin. The hydrophobic benzyl group in the d-Phe residue of cilengitide (3), for instance, was replaced by the strongly hydrophilic 1,2-dihydroxyethyl moiety in the mimetic 4a or by the poorly hydrophobic methyl group in compound 4b. Conversely, the hydrophobic R–R substituents Figure 1. Signaling pathways initiated by integrins affecting the gene regulation of angiogenesis. ERK=extracellular-signal-regulated kinase, FAK= focal adhesion kinase, FoxO= forkhead box O, JNK=c-Jun N-terminal kinase, NFkB=nuclear factor k of B-cells.

Catalyst-controlled enantioselective nitroaldol (or Henry) reactions are presented. These reactions represent powerful C–C bond-forming tools and the resulting nitro alcohol (nitroaldol) products can be transformed into a number of nitrogen- and oxygen-containing derivatives (nitroalkenes, amino alcohols, amino acids etc.). In addition to substrate-controlled nitroaldol reactions (not covered), catalytic systems that provide good stereoselectivity have been developed in recent years. Through the use of preformed silyl nitronates as activated substrates, catalytic systems involving metallic Lewis acids or tetraalkylammonium salts have been deployed in fluoride-mediated nitroaldol reactions. In a further advance, catalytic systems capable of promoting direct nitroaldol reactions between unmodified nitroalkanes and aldehydes (ketones) with high yields and stereoselectivities have been developed. To this end, ambifunctional systems based on La, Zn, Cu, Co and Mg metal species are described, together with some organocatalysts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

In situ generated azomethines from readily available precursors react with nitromethane in the presence of 120 mol % of CsOH·H2O and 12 mol % of quinine- and cinchonidine-derived quaternary ammonium chlorides to provide the corresponding aza-Henry adducts in good yields and very high selectivities. It represents the first general enantioselective aza-Henry method for azomethines derived from enolizable aldehydes, giving rise to enantiomeric excesses above 94%. In addition, the reactions with nitroethane afforded high diastereo- and enantioselectivities (syn:anti up to 95:5; up to 98% ee for syn).