Abacavir increases purinergic P2X7 receptor activation by ATP: does a pro-inflammatory synergism underlie its cardiovascular toxicity?

16 p.-9 fig.-1 tab.The cardiovascular toxicity of Abacavir is related to its purinergic structure. Purinergic P2X7-receptors (P2X7R), characterized by activation by high concentrations of ATP and with high plasticity, seem implicated. We appraise the nature of the interplay between Abacavir and P2X7R in generating vascular inflammation. The effects of Abacavir on leukocyte-endothelium interactions were compared with those of its metabolite carbovir triphosphate (CBV-TP) or ATP in the presence of apyrase (ATP-ase) or A804598 (P2X7R-antagonist). CBV-TP and ATP levels were evaluated by HPLC, while binding of Abacavir, CBV-TP and ATP to P2X7R was assessed by radioligand and docking studies. Hypersensitivity studies explored a potential allosteric action of Abacavir. Clinical concentrations of Abacavir (20 µmol/L) induced leukocyte-endothelial cell interactions by specifically activating P2X7R, but the drug did not show affinity for the P2X7R ATP-binding site (site 1). CBV-TP levels were undetectable in Abacavir-treated cells, while those of ATP were unaltered. The effects of Abacavir were Apyrase-dependent, implying dependence on endogenous ATP. Exogenous ATP induced a profile of proinflammatory actions similar to Abacavir, but was not entirely P2X7R-dependent. Docking calculations suggested ATP-binding to sites 1 and 2, and Abacavir-binding only to allosteric site 2. A combination of concentrations of Abacavir (1 µmol/L) and ATP (0.1 µmol/L) that had no effect when administered separately induced leukocyte-endothelium interactions mediated by P2X7R and involving Connexin43 channels. Therefore, Abacavir acts as a positive allosteric modulator of P2X7R, turning low concentrations of endogenous ATP themselves incapable of stimulating P2X7R into a functional proinflammatory agonist of the receptor.This work was supported by Ministerio de Economía y Competitividad and the European Regional Development fund of the European Union (FEDER) (SAF2015–67678-R, RTI2018-094436-B-I00 and CTQ2017-88353-R), Ministerio de Sanidad y Consumo (CB06/04/0071, CIBERehd) and Generalitat Valenciana (PROMETEOII/2014/035 and PROMETEO 2018/141), along with an unrestricted grant from GILEAD S.L. VCD and ASL were funded by VALI + D program from Generalitat Valenciana (grants number ACIF/2015/316 and ACIF/2016/119, respectively) and PGM by FPU program from Ministerio de Educación, Cultura y Deporte (grant number FPU16/06064) and MABR by FPU program from Ministerio de Ciencia, Innovación y Universidades (grant number FPU17/04249).Peer reviewe

Faceted phospholipid vesicles tailored for the delivery of Santolina insularis essential oil to the skin

The aim of this work was to formulate Santolina insularis essential oil-loaded nanocarriers, namely Penetration Enhancer containing Vesicles (PEVs), evaluate the physico-chemical features and stability, and gain insights into their ability to deliver the oil to the skin.S. insularis essential oil was obtained by steam distillation, and was predominantly composed of terpenes, the most abundant being β-phellandrene (22.6%), myrcene (11.4%) and curcumenes (12.1%). Vesicles were prepared using phosphatidylcholine, and ethylene or propylene glycol were added to the water phase (10% (v/v)) to improve vesicle performances as delivery systems. Vesicles were deeply characterized by light scattering, cryogenic transmission electron microscopy and small/wide-angle X-ray scattering, the results showing polyhedral, faceted, unilamellar vesicles of ~115. nm in size. The presence of the glycols improved vesicle stability under accelerated ageing conditions, without changes in size or migration phenomena (e.g. sedimentation and creaming). Confocal laser scanning microscopy images of pig skin treated with S. insularis formulations displayed a penetration ability of PEVs greater than that of control liposomes. Moreover, all formulations showed a marked in vitro biocompatibility in human keratinocytes.These findings suggest that the nanoformulation may be of value in enhancing the delivery of S. insularis essential oil to the skin, where it can exert its biological activities.SAXS/WAXS experiments were performed at the BL11-NCD beamline at ALBA Synchrotron with the collaboration of ALBA staff. The beamtime at ALBA was kindly provided within the approved proposal n. 2013110789. This work was supported by a grant from Programma di Sviluppo Rurale 2007-2013 PSR Sardegna-MISURA 124, NANOFITOCARE, determinazione n. 4230/14. Dr. Pons acknowledges financial support from MINECO-CTQ2013-41514-P.Peer reviewe