Title : Encapsulated natural molecules (flavonoids and stilbenoids) and model system-based cell death induction -focus on liposomes and cell/cell-free ghosts-based delivery systems
Abstract:
As per the WHO statistics, approximately 60% of the currently available anti-cancer chemotherapeutics are natural in origin. Flavonoids and Terpenoids constitute a distinct subset of such natural molecules. These molecules, found in various fruits and vegetables and other plant sources, have been extensively studied for their anti-oxidant potential, cytotoxicity and stress-induced cell death potential. However, seasonal variations as well as the possible loss of bioactive components (as a result of cooking and/or heat-induced food processing), the molecules would perforce have to be synthesized (using templates from Mother Nature). Such commercially available synthesized derivatives can be tested in model systems. Luteolin, a polyphenolic flavone, has been widely researched into for its antioxidant, cytotoxicity and cell death properties. We have demonstrated increased Luteolin-mediated in vitro antioxidant potential; cytotoxicity as well as cell death induction in HaCaT cells (in an immortalized skin cell line isolated from an adult). Due to its hydrophobic nature (Log P ~2.5), we felt a need to encapsulate this molecule and improve its cell death potential, by its enhanced uptake through the cell membrane phospholipid bilayer with a concomitant decrement in the dose/concentration. We have demonstrated that the liposome-encapsulated variant increased cytotoxicity and cell death induction, based on statistically significant increases in the activity of human caspase-3 and human caspase-14 (an enzyme, with a restricted tissue distribution, and expressed in the cornifying layer of human skin, apart from its expression in HaCaT and MCF-7 cells). Pterostilbene (a natural molecule present in the berries as well as grape leaves and vines) is another hydrophobic molecule (Log P ~3.69) in the stilbenoid category. Again, its hydrophobic nature prompted us to synthesize DOTAP-liposome-encapsulated Pterostilbene and preliminary screening has shown an increased cell death induction potential, correlated with a paradoxical dose-dependent decrement in the activity of human caspase-14 (increasing with increasing levels linked to human breast cancer tumorigenesis). This data set needs to be validated in 3D systems (considered to be better mimics of the tumor mimicking the hypoxic/necrotic core, followed by the quiescent and proliferative cells closer to the surface of the cell aggregates). This 3D system, when enriched for stem cells, would be a more realistic model for evaluating the chemotherapeutic potential of flavonoids, stilbenoids and their liposome-encapsulated variants. In addition, organoid models, that incorporate the vasculature as well as the immune components, would be superior in predicting the toxicity and cell death potential of our molecule-nano-construct combination. In order to overcome the inherent limitations of the liposome-encapsulation strategy, MSC, erythrocyte -ghost (produced from the cell membranes of) exhibit tropism towards the desired target (based on the cells-of-origin of these nano-ghosts, apart from them being biocompatible and immune-tolerant, thereby making them excellent candidates for specifically testing ghost-encapsulated Luteolin and/or Pterostilbene in our higher order model systems. Exosomal ghost (synthetic or natural) derived from membrane-bound vesicles that are known to be involved endogenously in cell-cell communication can also be employed for their drug delivery capabilities, since they will be tolerated by our immune system and are biocompatible in nature with tropism properties.
