Discerning perturbed assembly of lipids in a model membrane in presence of violacein

Modulating a model membrane of sphingomyelin by a tricyclic antidepressant drug

Tricyclic medicine such as amitriptyline (AMT) hydrochloride, initially developed to treat depression, is also used to treat neuropathic pain, anxiety disorder, and migraines. The mechanism of functioning of this type of drugs is ambiguous. Understanding the mechanism is important for designing new drug molecules with higher pharmacological efficiency. Hence, in the present study, biophysical approaches have been taken to shed light on their interactions with a model cellular membrane of brain sphingomyelin in the form of monolayer and multi-lamellar vesicles. The surface pressure-area isotherm infers the partitioning of a drug molecule into the lipid monolayer at the air water interface, providing a higher surface area per molecule and reducing the in-plane elasticity. Further, the surface electrostatic potential of the lipid monolayer is found to increase due to the insertion of drug molecule. The interfacial rheology revealed a reduction of the in-plane viscoelasticity of the lipid film, which, depends on the adsorption of the drug molecule onto the film. Small-angle X-ray scattering (SAXS) measurements on multilamellar vesicles (MLVs) have revealed that the AMT molecules partition into the hydrophobic core of the lipid membrane, modifying the organization of lipids in the membrane. The modified physical state of less rigid membrane and the transformed electrostatics of the membrane could influence its interaction with synaptic vesicles and neurotransmitters making higher availability of the neurotransmitters in the synaptic cleft.

Antitumor activity of natural pigment violacein against osteosarcoma and rhabdomyosarcoma cell lines

PURPOSE

Sarcomas are rare and heterogenic tumors with unclear etiology. They develop in bone and connective tissue, mainly in pediatric patients. To increase efficacy of current therapeutic options, natural products showing selective toxicity to tumor cells are extensively investigated. Here, we evaluated antitumor activity of bacterial pigment violacein in osteosarcoma (OS) and rhabdomyosarcoma (RMS) cell lines.

METHODS

The toxicity of violacein was assessed in vitro and in vivo, using MTT assay and FET test. The effect of violacein on cell migration was monitored by wound healing assay, cell death by flow cytometry, uptake of violacein by fluorescence microscopy, generation of reactive oxygen species (ROS) by DCFH-DA assay and lipid peroxidation by TBARS assay.

RESULTS

Violacein IC50 values for OS and RMS cells were in a range from 0.35 to 0.88 µM. Its selectivity toward malignant phenotype was confirmed on non-cancer V79-4 cells, and it was safe in vivo, for zebrafish embryos in doses up to 1 µM. Violacein induced apoptosis and affected the migratory potential of OS and RMS cells. It was found on the surfaces of tested cells. Regarding the mechanism of action, violacein acted on OS and RMS cells independently of oxidative signaling, as judged by no increase in intracellular ROS generation and no lipid peroxidation.

CONCLUSION

Our study provided further evidence that reinforces the potential of violacein as an anticancer agent and candidate to consider for improvement of the effectiveness of traditional OS and RMS therapies.

Discerning perturbed assembly of lipids in a model membrane in presence of violacein: Effects of membrane hydrophobicity

For the lack of effective antibiotics towards antibiotic resisting bacteria, it is required to discover new antibiotics and to understand their antimicrobial mechanism. Violacein is a violet pigment found in several gram-negative bacteria possessing antimicrobial properties to gram-positive bacteria. This present article investigates the insertion ability of this molecule into a model membrane composed of zwitterionic phospholipids. Thermodynamic characterization of lipid monolayers in the presence of violacein was carried out using a single lipid layer formed at air-water interface. The molecule inserts into the layer altering the area occupied by each lipid and the in-plane compressibility of the film. This insertion increases with the hydrophobic chain length of the lipid. The perturbed self-assembly of lipids in a bilayer is quantified using a lipid multilayer system applying the X-ray reflectivity technique. The electron density profile from the reflectivity data shows that the molecule inserts into the fluid phase creating a relatively ordered chain conformation. Further, the insertion into the gel phase is observed to increase with the increased thickness of the hydrophobic core of a bilayer.

Enzymatic Active Release of Violacein Present in Nanostructured Lipid Carrier by Lipase Encapsulated in 3D-Bioprinted Chitosan-Hydroxypropyl Methylcellulose Matrix With Anticancer Activity

Violacein (Viol) is a bacterial purple water-insoluble pigment synthesized by Chromobacterium violaceum and other microorganisms that display many beneficial therapeutic properties including anticancer activity. Viol was produced, purified in our laboratory, and encapsulated in a nanostructured lipid carrier (NLC). The NLC is composed of the solid lipid myristyl myristate, an oily lipid mixture composed of capric and caprylic acids, and the surfactant poloxamer P188. Dormant lipase from Rhizomucor miehei was incorporated into the NLC-Viol to develop an active release system. The NLC particle size determined by dynamic light scattering brings around 150 nm particle size and ζ≈ −9.0 mV with or without lipase, but the incorporation of lipase increase the PdI from 0.241 to 0.319 (≈32%). For scaffold development, a 2.5 hydroxypropyl methylcellulose/chitosan ratio was obtained after optimization of a composite for extrusion in a 3D-bioprinter developed and constructed in our laboratory. Final Viol encapsulation efficiency in the printings was over 90%. Kinetic release of the biodye at pH = 7.4 from the mesh containing NLC-lipase showed roughly 20% Viol fast release than without the enzyme. However, both Viol kinetic releases displayed similar profiles at pH = 5.0, where the lipase is inactive. The kinetic release of Viol from the NLC-matrices was modeled and the best correlation was found with the Korsmeyer-Peppas model (R2 = 0.95) with n < 0.5 suggesting a Fickian release of Viol from the matrices. Scanning Electron Microscope (SEM) images of the NLC-meshes showed significant differences before and after Viol’s release. Also, the presence of lipase dramatically increased the gaps in the interchain mesh. XRD and Fourier Transform Infrared (FTIR) analyses of the NLC-meshes showed a decrease in the crystalline structure of the composites with the incorporation of the NLC, and the decrease of myristyl myristate in the mesh can be attributed to the lipase activity. TGA profiles of the NLC-meshes showed high thermal stability than the individual components. Cytotoxic studies in A549 and HCT-116 cancer cell lines revealed high anticancer activity of the matrix mediated by mucoadhesive chitosan, plus the biological synergistic activities of violacein and lipase.

Mechanistic Understanding from Molecular Dynamics in Pharmaceutical Research 2: Lipid Membrane in Drug Design

We review the use of molecular dynamics (MD) simulation as a drug design tool in the context of the role that the lipid membrane can play in drug action, i.e., the interaction between candidate drug molecules and lipid membranes. In the standard "lock and key" paradigm, only the interaction between the drug and a specific active site of a specific protein is considered; the environment in which the drug acts is, from a biophysical perspective, far more complex than this. The possible mechanisms though which a drug can be designed to tinker with physiological processes are significantly broader than merely fitting to a single active site of a single protein. In this paper, we focus on the role of the lipid membrane, arguably the most important element outside the proteins themselves, as a case study. We discuss work that has been carried out, using MD simulation, concerning the transfection of drugs through membranes that act as biological barriers in the path of the drugs, the behavior of drug molecules within membranes, how their collective behavior can affect the structure and properties of the membrane and, finally, the role lipid membranes, to which the vast majority of drug target proteins are associated, can play in mediating the interaction between drug and target protein. This review paper is the second in a two-part series covering MD simulation as a tool in pharmaceutical research; both are designed as pedagogical review papers aimed at both pharmaceutical scientists interested in exploring how the tool of MD simulation can be applied to their research and computational scientists interested in exploring the possibility of a pharmaceutical context for their research.

Multi-target drug with potential applications: violacein in the spotlight

The aim of the current review is to address updated research on a natural pigment called violacein, with emphasis on its production, biological activity and applications. New information about violacein's action mechanisms as antitumor agent and about its synergistic action in drug delivery systems has brought new alternatives for anticancer therapy. Thus, violacein is introduced as reliable drug capable of overcoming at least three cancer hallmarks, namely: proliferative signaling, cell death resistance and metastasis. In addition, antimicrobial effects on several microorganisms affecting humans and other animals turn violacein into an attractive drug to combat resistant pathogens. Emphasis is given to effects of violacein combined with different agents, such as antibiotics, anticancer agents and nanoparticles. Although violacein is well-known for many decades, it remains an attractive compound. Thus, research groups have been making continuous effort to help improving its production in recent years, which can surely enable its pharmaceutical and chemical application as multi-task compound, even in the cosmetics and food industries.