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Background: Doxorubicin (DOX) has been very effective against glioblastoma invitro. Its application in vivo is hampered because it cannot pass the blood–brainbarrier (BBB). Significant research efforts are invested to overcome this limitation.Sclareol (SC) is an aromatic compound naturally found in clary sage. Thecombination of SC and DOX showed promising effects in different tumor types invitro and in vivo. Therefore, we tested their combination and innovative hybridmolecules (SC:DOX) on glioblastoma cells with the expression of P-glycoprotein, amajor component of BBB and cancer multidrug resistance marker. Methods:Cytotoxicity and selectivity towards glioblastoma cells of SC, DOX, theircombination, and SC:DOX were examined by MTT assay. The effect of SC on DOXaccumulation was determined by flow cytometry. We also studied SC:DOXaccumulation, cellular uptake, localization imaging, and DNA damage induction.Results: The effects of simultaneous SC and DOX treatments demonstrated theconsiderable potential of SC to reverse DOX resistance in glioblastoma cells andincrease DOX accumulation. SC:DOX hybrids, named CON1 and CON2 were lesscytotoxic than DOX, but with reduced resistance and increased selectivity towardsglioblastoma cells. Cellular uptake of CON1 and CON2 was increased in glioblastomacells compared to DOX. Perinuclear localization of CON1 and CON2 vs. nuclearlocalization of DOX as well as no DNA damaging effects suggest a differentmechanism of action for SC:DOX. Conclusion: The combination of SC and DOX, andtheir innovative hybrids, could be considered a promising strategy that can overcomethe limitations of DOX application in glioblastoma.

There is accumulating evidence demonstrating effects of gastrointestinal microbiota on brain function and behavior, including depressive behavior. We have demonstrated that antidepressants, the main drugs used for alleviating depression, affect gut microbiota composition as well, and in this way partly contribute to improvement of depressive symptoms. Specifically, our results showed that several types of antidepressants reduced abundance of bacterial genera Ruminococcus, while supplementation with R. flavefaciens diminished antidepressant-induced decrease of depressive behavior. Treatment with R. flavefaciens affected cortical gene networks, up-regulating genes involved in mitochondrial oxidative phosphorylation, while down-regulating genes involved in neuronal plasticity, suggesting a mechanism for microbial regulation of antidepressant treatment efficiency. In further studies, we are aiming to delineate the role of gut microbiota in conveying the long-term effects of adolescent stress on development of anxiety and depressive behavior.