Abacavir Increases Purinergic P2X7 Receptor Activation by ATP: Does a Pro-inflammatory Synergism Underlie Its Cardiovascular Toxicity?

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.

Tenofovir-induced toxicity in renal proximal tubular epithelial cells: involvement of mitochondria.

OBJECTIVE: In-vivo studies suggest that mitochondria is involved in tenofovir (TFV)-induced renal toxicity, but the underlying mechanisms are still unclear. The aim of the present study was to assess the effects of TFV and its prodrug, TFV disoproxil fumarate, on mitochondrial function and cell survival/viability in a renal proximal tubular cell line. DESIGN AND METHODS: We evaluated parameters of cellular proliferation/survival (cell count, cell cycle, viability) and mitochondrial function (oxygen consumption, mitochondrial membrane potential, reactive oxygen species production) in NRK-52E cells. Intracellular TFV was measured by HPLC and expression of antioxidant genes was analysed by real-time PCR. RESULTS: Similar intracellular levels of TFV were reached with lower concentrations of the prodrug than of the drug, and correlated directly with a decrease in cell number. Both compounds inhibited proliferation and compromised mitochondrial function by decreasing mitochondrial membrane potential and increasing oxygen consumption and mitochondrial superoxide production. Altered oxidative status was confirmed by the overexpression of antioxidant genes. CONCLUSIONS: Intracellular accumulation of TFV induces mitochondrial toxicity in an in-vitro renal model and alters cell proliferation and viability. Our findings call for caution regarding the use of this nucleotide analogue reverse transcriptase inhibitor in patients with other risk factors that compromise mitochondrial function in the kidney.

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 ß-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.

Rate and extent of oxaliplatin absorption after hyperthermic intraperitoneal administration in peritoneal carcinomatosis patients.

PURPOSE: To determine the rate and extent of hyperthermic intraperitoneal oxaliplatin (HIO) absorption in peritoneal carcinomatosis patients treated with cytoreductive surgery (CRS) and the effect of the isotonic carrier solution on HIO absorption parameters. METHODS: Full pharmacokinetic profiles collected in peritoneum and plasma from 57 subjects treated with CRS followed by 30 min of HIO were pooled with sparse plasma concentrations collected from 50 patients with solid tumors treated with intravenous oxaliplatin. Pharmacokinetic data were jointly analyzed with nonlinear mixed-effect model (NONMEM VII software). The effect of carrier solution (icodextrin 4 % vs. dextrose 5 %) and selected patient covariates on oxaliplatin pharmacokinetics was investigated. Model evaluation was performed using predictive checks and nonparametric bootstrap. RESULTS: An open linear two-compartment disposition model with linear absorption from peritoneum to plasma was used to characterize the oxaliplatin pharmacokinetics in peritoneum and plasma. No patient-related covariates were associated with oxaliplatin pharmacokinetics. The volume of distribution in the peritoneum (V a) exponentially decreased due to the carrier solute absorption. The reduction in V a was 1.76-fold faster when HIO was administered in dextrose 5 %, relative to icodextrin 4 %. For HIO durations of 30 min, the rate of oxaliplatin absorption ranges from 0.84 to 0.96 h(-1) for icodextrin 4 % and from 0.86 to 1.09 h(-1) for dextrose 5 %. The extent of HIO absorption was 38 %, regardless of the carrier solution. CONCLUSIONS: Hyperthermic intraperitoneal oxaliplatin absorption is fast and incomplete. The small difference in oxaliplatin exposure between both carrier solutions evaluated is not clinically relevant for HIO durations of 30 min.