Synthesis, Characterization, and In Vitro Insulin-Mimetic Activity Evaluation of Valine Schiff Base Coordination Compounds of Oxidovanadium(V)

MD Simulations to Calculate NMR Relaxation Parameters of Vanadium(IV) Complexes: A Promising Diagnostic Tool for Cancer and Alzheimer's Disease

Early phase diagnosis of human diseases has still been a challenge in the medicinal field, and one of the efficient non-invasive techniques that is vastly used for this purpose is magnetic resonance imaging (MRI). MRI is able to detect a wide range of diseases and conditions, including nervous system disorders and cancer, and uses the principles of NMR relaxation to generate detailed internal images of the body. For such investigation, different metal complexes have been studied as potential MRI contrast agents. With this in mind, this work aims to investigate two systems containing the vanadium complexes [VO(metf)2]·H2O (VC1) and [VO(bpy)2Cl]+ (VC2), being metformin and bipyridine ligands of the respective complexes, with the biological targets AMPK and ULK1. These biomolecules are involved in the progression of Alzheimer's disease and triple-negative breast cancer, respectively, and may act as promising spectroscopic probes for detection of these diseases. To initially evaluate the behavior of the studied ligands within the aforementioned protein active sites and aqueous environment, four classical molecular dynamics (MD) simulations including VC1 + H2O (1), VC2 + H2O (2), VC1 + AMPK + H2O (3), and VC2 + ULK1 + H2O (4) were performed. From this, it was obtained that for both systems containing VCs and water only, the theoretical calculations implied a higher efficiency when compared with DOTAREM, a famous commercially available contrast agent for MRI. This result is maintained when evaluating the system containing VC1 + AMPK + H2O. Nevertheless, for the system VC2 + ULK1 + H2O, there was observed a decrease in the vanadium complex efficiency due to the presence of a relevant steric hindrance. Despite that, due to the nature of the interaction between VC2 and ULK1, and the nature of its ligands, the study gives an insight that some modifications on VC2 structure might improve its efficiency as an MRI probe.

Chemical Attachment of 5-Nitrosalicylaldimine Motif to Silatrane Resulting in an Organic-Inorganic Structure with High Medicinal Significance

Two chemical motifs of interest for medicinal chemistry, silatrane as 1-(3-aminopropyl) silatrane (SIL M), and nitro group attached in position 5 to salicylaldehyde, are coupled in a new structure, 1-(3-{[(2-hydroxy-5-nitrophenyl)methylidene]amino}propyl)silatrane (SIL-BS), through an azomethine moiety, also known as a versatile pharmacophore. The high purity isolated compound was structurally characterized by an elemental, spectral, and single crystal X-ray diffraction analysis. Given the structural premises for being a biologically active compound, different specific techniques and protocols have been used to evaluate their in vitro hydrolytic stability in simulated physiological conditions, the cytotoxicity on two cancer cell lines (HepG2 and MCF7), and protein binding ability-with a major role in drug ADME (Absorption, Distribution, Metabolism and Excretion), in parallel with those of the SIL M. While the latter had a good biocompatibility, the nitro-silatrane derivative, SIL-BS, exhibited a higher cytotoxic activity on HepG2 and MCF7 cell lines, performance assigned, among others, to the known capacity of the nitro group to promote a specific cytotoxicity by a "activation by reduction" mechanism. Both compounds exhibited increased bio- and muco-adhesiveness, which can favor an optimized therapeutic effect by increased drug permeation and residence time in tumor location. Additional benefits of these compounds have been demonstrated by their antimicrobial activity on several fungi and bacteria species. Molecular docking computations on Human Serum Albumin (HSA) and MPRO COVID-19 protease demonstrated their potential in the development of new drugs for combined therapy.

Heteroleptic oxidovanadium(IV)-malate complex improves glucose uptake in HepG2 and enhances insulin action in streptozotocin-induced diabetic rats

Diabetes mellitus, a complex and heterogeneous disease associated with hyperglycemia, is a leading cause of mortality and reduces life expectancy. Vanadium complexes have been studied for the treatment of diabetes. The effect of complex [VO(bpy)(mal)]·H₂O (complex A) was evaluated in a human hepatocarcinoma (HepG2) cell line and in streptozotocin (STZ)-induced diabetic male Wistar rats conditioned in seven groups with different treatments (n = 10 animals per group). Electron paramagnetic resonance and ⁵¹V NMR analyses of complex A in high-glucose Dulbecco's Modified Eagle Medium (DMEM) revealed the oxidation and hydrolysis of the oxidovanadium(IV) complex over a period of 24 h at 37 °C to give low-nuclearity vanadates "V1" (H₂VO₄^-), "V2" (H₂V₂O₇^2-), and "V4" (V₄O₁₂^4-). In HepG2 cells, complex A exhibited low cytotoxic effects at concentrations 2.5 to 7.5 μmol L^-1 (IC₅₀ 10.53 μmol L^-1) and increased glucose uptake (2-NBDG) up to 93%, an effect similar to insulin. In STZ-induced diabetic rats, complex A at 10 and 30 mg kg^-1 administered by oral gavage for 12 days did not affect the animals, suggesting low toxicity or metabolic impairment during the experimental period. Compared to insulin treatment alone, complex A (30 mg kg^-1) in association with insulin was found to improve glycemia (30.6 ± 6.3 mmol L^-1 vs. 21.1 ± 8.6 mmol L^-1, respectively; p = 0.002), resulting in approximately 30% additional reduction in glycemia. The insulin-enhancing effect of complex A was associated with low toxicity and was achieved via oral administration, suggesting the potential of complex A as a promising candidate for the adjuvant treatment of diabetes.

Antitumor Properties of a New Macrocyclic Tetranuclear Oxidovanadium(V) Complex with 3-Methoxysalicylidenvaline Ligand

A wide variety of metal-based compounds have been obtained and studied for their antitumor activity since the intensely used cytostatic drugs (e.g., cisplatin) failed to accomplish their expected pharmacological properties. Thus, we aimed to develop a new vanadium-based drug and assess its antitumor properties using the human hepatocarcinoma (HepG2) cell line. The compound was synthesized from vanadyl sulfate, DL-valine, and o-vanillin and was spectrally and structurally characterized (UV-Vis, IR, CD, and single-crystal/powder-XRD). Compound stability in biological media, cell uptake, and the interaction with albumin were assessed. The mechanisms of its antitumor activity were determined compared to cisplatin by performing cytotoxicity, oxidative and mitochondrial status, DNA fragmentation, β-Tubulin synthesis investigation, and cell cycle studies. Herein, we developed a macrocyclic tetranuclear oxidovanadium(V) compound, [(V^VO)(L)(CH₃O)]₄, having coordinated four Schiff base (H₂L) ligands, 3-methoxysalicylidenvaline. We showed that [(V^VO)(L)(CH₃O)]₄: (i) has pH-dependent stability in biological media, (ii) binds to albumin in a dose-dependent manner, (iii) is taken up by cells in a time-dependent way, (iv) has a higher capacity to induce cell death compared to cisplatin (IC₅₀ = 6 μM vs. 10 μM), by altering the oxidative and mitochondrial status in HepG2 cells. Unlike cisplatin, which blocks the cell cycle in the S-phase, the new vanadium-based compound arrests it in S and G2/M-phase, whereas no differences in the induction of DNA fragmentation and reduction of β-Tubulin synthesis between the two were determined. Thus, the [(V^VO)(L)(CH₃O)]₄ antitumor mechanism involved corroboration between the generation of oxidative species, mitochondrial dysfunction, degradation of DNA, cell cycle arrest in the S and G2/M-phase, and β-Tubulin synthesis reduction. Our studies demonstrate the potent antitumor activity of [(V^VO)(L)(CH₃O)]₄ and propose it as an attractive candidate for anticancer therapy.

Bio-Responsive Carriers for Controlled Delivery of Doxorubicin to Cancer Cells

The cellular internalization of drug carriers occurs via different endocytic pathways that ultimately involve the endosomes and the lysosomes, organelles where the pH value drops to 6.0 and 5.0, respectively. We aimed to design and characterize pH/temperature-responsive carriers for the effective delivery of the anti-tumoral drug doxorubicin. To this purpose, poly(N-isopropylacrylamide-co-vinylimidazole) was synthesized as an attractive pH/temperature-sensitive copolymer. Microspheres made of this copolymer, loaded with doxorubicin (MS-DXR), disintegrate in monodisperse nanospheres (NS-DXR) under conditions similar to that found in the bloodstream (pH = 7.4, temperature of 36 °C) releasing a small amount of payload. However, in environments that simulate the endosomal and lysosomal conditions, nanospheres solubilize, releasing the entire amount of drug. We followed the NS-DXR internalization using two cancer cell lines, hepatic carcinoma HepG2 cells and lung adenocarcinoma A549 cells. The data showed that NS-DXR are internalized to a greater extent by HepG2 cells than A549 cells, and this correlated with increased cytotoxicity induced by NS-DXR in HepG2 cells compared with A549 cells. Moreover, NS-DXR particles do not cause hemolysis and erythrocytes aggregation. Administered in vivo, NS-DXR localized in the liver and kidneys of mice, and the loading of DXR into NS resulted in the reduced renal clearance of DXR. In conclusion, the newly developed poly(N-isopropylacrylamide-co-vinyl imidazole) particles are biocompatible and may be introduced as carriers for doxorubicin to hepatic tumors.

Targeting Breast Cancer and Their Stem Cell Population through AMPK Activation: Novel Insights

Despite some significant advancements, breast cancer has become the most prevalent cancer in the world. One of the main reasons for failure in treatment and metastasis has been attributed to the presence of cancer initiating cells—cancer stem cells. Consequently, research is now being focussed on targeting cancer cells along with their stem cell population. Non-oncology drugs are gaining increasing attention for their potent anticancer activities. Metformin, a drug commonly used to treat type 2 diabetes, is the best example in this regard. It exerts its therapeutic action by activating 5′ adenosine monophosphate-activated protein kinase (AMPK). Activated AMPK subsequently phosphorylates and targets several cellular pathways involved in cell growth and proliferation and the maintenance of stem-like properties of cancer stem cells. Therefore, AMPK is emerging as a target of choice for developing effective anticancer drugs. Vanadium compounds are well-known PTP inhibitors and AMPK activators. They find extensive applications in treatment of diabetes and obesity via PTP1B inhibition and AMPK-mediated inhibition of adipogenesis. However, their role in targeting cancer stem cells has not been explored yet. This review is an attempt to establish the applications of insulin mimetic vanadium compounds for the treatment of breast cancer by AMPK activation and PTP1B inhibition pathways.

Development of Dextran-Coated Magnetic Nanoparticles Loaded with Protocatechuic Acid for Vascular Inflammation Therapy

Vascular inflammation plays a crucial role in the progression of various pathologies, including atherosclerosis (AS), and thus it has become an attractive therapeutic target. The protocatechuic acid (PCA), one of the main metabolites of complex polyphenols, is endowed with anti-inflammatory activity, but its formulation into nanocarriers may increase its bioavailability. In this study, we developed and characterized dextran shell‒iron oxide core nanoparticles loaded with PCA (MNP-Dex/PCA) and assessed their cytotoxicity and anti-inflammatory potential on cells acting as key players in the onset and progression of AS, namely, endothelial cells (EC) and monocytes/macrophages. The results showed that MNP-Dex/PCA exert an anti-inflammatory activity at non-cytotoxic and therapeutically relevant concentrations of PCA (350 μM) as supported by the reduced levels of inflammatory molecules such as MCP-1, IL-1β, TNF-α, IL-6, and CCR2 in activated EC and M1-type macrophages and functional monocyte adhesion assay. The anti-inflammatory effect of MNP-Dex/PCA was associated with the reduction in the levels of ERK1/2 and p38-α mitogen-activated protein kinases (MAPKs) and NF-kB transcription factor. Our data support the further development of dextran shell-magnetic core nanoparticles as theranostic nanoparticles for guidance, imaging, and therapy of vascular inflammation using PCA or other anti-inflammatory compounds.

Study of DNA Interaction and Cytotoxicity Activity of Oxidovanadium(V) Complexes with ONO Donor Schiff Base Ligands

Two new oxidovanadium(V) complexes, (HNEt3)[VVO2L] (1) and [(VVOL)2μ-O] (2), have been synthesized using a tridentate Schiff base ligand H2L [where H2L = 4-((E)-(2-hydroxy-5-nitrophenylimino)methyl)benzene-1,3-diol] and VO(acac)2 as starting metal precursor. The ligand and corresponding metal complexes are characterized by physicochemical (elemental analysis), spectroscopic (FT-IR, UV–Vis, and NMR), and spectrometric (ESI–MS) methods. X-ray crystallographic analysis indicates the anion in salt 1 features a distorted square-pyramidal geometry for the vanadium(V) center defined by imine-N, two phenoxide-O, and two oxido-O atoms. The interaction of the compounds with CT–DNA was studied through UV–Vis absorption titration and circular dichroism methods. The results indicated that complexes showed enhanced binding affinity towards DNA compared to the ligand molecule. Finally, the in vitro cytotoxicity studies of H2L, 1, and 2 were evaluated against colon cancer (HT-29) and mouse embryonic fibroblast (NIH-3T3) cell lines by MTT assay. The results demonstrated that the compounds manifested a cytotoxic potential comparable with clinically referred drugs and caused cell death by apoptosis.