by Keyword: Cytotoxicity

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Ikonomov, O. C., Altankov, G., Sbrissa, D., Shisheva, A., (2018). PIKfyve inhibitor cytotoxicity requires AKT suppression and excessive cytoplasmic vacuolation Toxicology and Applied Pharmacology 356, 151-158

PIKfyve phosphoinositide kinase produces PtdIns(3,5)P2 and PtdIns5P and governs a myriad of cellular processes including cytoskeleton rearrangements and cell proliferation. The latter entails rigorous investigation since the cytotoxicity of PIKfyve inhibition is a potential therapeutic modality for cancer. Here we report the effects of two PIKfyve-specific inhibitors on the attachment/spreading and viability of mouse embryonic fibroblasts (MEFs) and C2C12 myoblasts. Importantly, 18-h treatment of adherent cells with YM201636 (800 nM) and apilimod (20 nM) in serum-containing culture media did not affect cell viability despite the presence of multiple cytoplasmic vacuoles, a hallmark of PIKfyve inhibition. Strikingly, at the same dose and duration the inhibitors caused excessive cytoplasmic vacuolation, initial suppression of cell attachment/spreading and subsequent marked detachment/death in serum-deprived cells. The remaining adherent cells under serum-deprived conditions had smaller surface area, lacked vinculin/actin-positive focal adhesions and displayed vacuoles occupying the entire cytoplasm. Serum or growth factors protected against PIKfyve inhibitor cytotoxicity. This protection required Akt activation evidenced by the abrogated beneficial effect of serum upon treatment with the clinically-relevant Akt inhibitor MK-2206. Moreover, Akt inhibition triggered cell detachment/death even in serum-fed adherent MEFs treated with apilimod. Intriguingly, BafilomycinA1 (H+-vacuolar ATPase inhibitor), which prevents the cytoplasmic vacuolation under PIKfyve perturbations, rescued all defects in attaching/spreading as well as in adherent cells under serum-starved or serum-fed conditions, respectively. Together, the results indicate that the cytotoxicity of PIKfyve inhibitors in MEFs and C2C12 myoblasts requires Akt suppression and excessive cytoplasmic vacuolation.

Keywords: AKT, Cytotoxicity, MK-2206, PIKfyve, Ppilimod, YM201636

Andrade, F., Neves, J. D., Gener, P., Schwartz, S., Ferreira, D., Oliva, M., Sarmento, B., (2015). Biological assessment of self-assembled polymeric micelles for pulmonary administration of insulin Nanomedicine: Nanotechnology, Biology, and Medicine 11, (7), 1621-1631

Pulmonary delivery of drugs for both local and systemic action has gained new attention over the last decades. In this work, different amphiphilic polymers (Soluplus®, Pluronic® F68, Pluronic® F108 and Pluronic® F127) were used to produce lyophilized formulations for inhalation of insulin. Development of stimuli-responsive, namely glucose-sensitive, formulations was also attempted with the addition of phenylboronic acid (PBA). Despite influencing the in vitro release of insulin from micelles, PBA did not confer glucose-sensitive properties to formulations. Lyophilized powders with aerodynamic diameter (<. 6. μm) compatible with good deposition in the lungs did not present significant in vitro toxicity for respiratory cell lines. Additionally, some formulations, in particular Pluronic® F127-based formulations, enhanced the permeation of insulin through pulmonary epithelial models and underwent minimal internalization by macrophages in vitro. Overall, formulations based on polymeric micelles presenting promising characteristics were developed for the delivery of insulin by inhalation. From the Clinical Editor: The ability to deliver other systemic drugs via inhalation has received renewed interests in the clinical setting. This is especially true for drugs which usually require injections for delivery, like insulin. In this article, the authors investigated their previously developed amphiphilic polymers for inhalation of insulin in an in vitro model. The results should provide basis for future in vivo studies.

Keywords: Cytotoxicity, Inhalation, Permeability, Phagocytosis, Polymeric micelles, Protein delivery