A natural anticancer pigment,Pheophytin a, from a seagrass acts as a high affinity human mitochondrial translocator protein (TSPO) ligand, in silico, to reduce mitochondrial membrane Potential (Δψmit) in adenocarcinomic A549 cells

Background: The present investigation looks at the most likely possibilities of usage of a naturally occurring photosynthetic pigment, Pheophytin a, from the seagrass, Syringodium isoetifolium, for plausible use as human TSPO ligand. Methods: Pheophytin a isolated in our laboratory previously was administered to A549 cell lines in vitro to examine its effects on cell migrations, DNA, cell cycle, Mitochondrial Membrane Potential and gene expressions. In silico tools were used to predict the nature of the compound and target binding. Results: Pheophytin a had IC50 values of 22.9 +/- 5.8 mu M for cancerous A549 cell lines, whilst not targeting non-cancerous vero cells [IC50: 183.6 +/- 1.92 mu M]. Pheophytin a hindered cellular migration, fragmented DNA, arrested cell cycle precisely at S phase, reduced Delta psi(mit) and directed mRNA expressions toward apoptosis. In silico tools indicate that the compound binds to TSPO with high effectiveness to collapse Delta psi(mit),(which is proved using wet lab experiments) to promote mitophagy. Conclusion: Hence Pheophytin a could be seen as a possible TSPO ligand for targeting metastatic alveolar cancers like A549 via intrinsic apoptotic pathway. General significance: Given the inherent non-toxic nature of the compound and easy extractability from almost all autotrophic eukaryotes, one could be confident to testing in animal models.