Encapsulation of α-Pinene in Delivery Systems Based on Liposomes and Cyclodextrins.

The essential oil component α-pinene has multiple biological activities. However, its application is limited owing to its volatility, low aqueous solubility, and chemical instability. For the aim of improving its physicochemical properties, α-pinene was encapsulated in conventional liposomes (CLs) and drug-in-cyclodextrin-in-liposomes (DCLs). Hydroxypropyl-ß-cyclodextrin/α-pinene (HP-ß-CD/α-pinene) inclusion complexes were prepared in aqueous solution, and the optimal solubilization of α-pinene occurred at HP-ß-CD:α-pinene molar ratio of 7.5:1. The ethanol-injection method was applied to produce different formulations using saturated (Phospholipon 90H) or unsaturated (Lipoid S100) phospholipids in combination with cholesterol. The size, the phospholipid and cholesterol incorporation rates, the encapsulation efficiency (EE), and the loading rate (LR) of α-pinene were determined, and the storage stability of liposomes was assessed. The results showed that α-pinene was efficiently entrapped in CLs and DCLs with high EE values. Moreover, Lipoid S100 CLs displayed the highest LR (22.9 ± 2.2%) of α-pinene compared to the other formulations. Both carrier systems HP-ß-CD/α-pinene inclusion complex and Lipoid S100 CLs presented a gradual release of α-pinene. Furthermore, the DPPH radical scavenging activity of α-pinene was maintained upon encapsulation in Lipoid S100 CLs. Finally, it was found that all formulations were stable after three months of storage at 4 °C.

Safety and Efficacy of New Oximes to Reverse Low Dose Diethyl-Paraoxon-Induced Ventilatory Effects in Rats.

BACKGROUND: Oximes are used in addition to atropine to treat organophosphate poisoning. However, the efficiency of oximes is still a matter of debate. In vitro experiments suggested than new oximes are more potent than the commercial oximes. However, the antidotal activity of new oximes has not been assessed in vivo. METHODS: The aim of this work was to assess the safety and efficiency of new oximes compared to pralidoxime in a rat model of diethyl paraoxon-induced non-lethal respiratory toxicity. RESULTS: Safety study of oximes showed no adverse effects on ventilation in rats. KO-33, KO-48, KO-74 oximes did not exhibit significant antidotal effect in vivo. In contrast, KO-27 and BI-6 showed evidence of antidotal activity by normalization of respiratory frequency and respiratory times. KO-27 became inefficient only during the last 30 min of the study. In contrast, pralidoxime demonstrated to be inefficient at 30 min post injection. Inversely, the antidotal activity of BI-6 occurred lately, within the last 90 min post injection. CONCLUSION: This study showed respiratory safety of new oximes. Regarding, the efficiency, KO-27 revealed to be a rapid acting antidote toward diethylparaoxon-induced respiratory toxicity, meanwhile BI-6 was a late-acting antidote. Simultaneous administration of these two oximes might result in a complete and prolonged antidotal efficiency.

P-glycoprotein modulates oleanolic acid effects in hepatocytes cancer cells and zebrafish embryos.

Oleanolic acid (OA) is a triterpenoid, widely found in plants and possesses antitumor activity in many cancer lines. However, cancer cells develop multidrug resistance (mdr) hindering the effect of anticancer drugs. P-glycoprotein (P-gp) is a major cause of mdr. Therefore, the cytotoxic effect of OA was evaluated on human breast cancer MDA-MB-231 and human liver cancer HepG2 with absence and presence of P-gp, respectively. OA reduced MDA-MB-231 viability in a dose dependent manner, whereas no remarkable effect was observed on HepG2 in the same range of concentrations (1-60 µM). Moreover, cytotoxicity studies were conducted in the presence of verapamil (20 mg/L), a P-gp inhibitor. OA exhibited the same effect on MDA-MB-231 in the absence and presence of verapamil. However, the cytotoxicity was greatly enhanced for HepG2 cells in the presence of verapamil (cell viability dropped from 63.7% to 25% after 72 h at 60 µM). The results were then confirmed in vivo on zebrafish embryos. Increased mortality and malformations were observed in verapamil pretreated group between 5 and 15 µM of OA compared to control; also, all embryos died at 20 µΜ OA and above. These results demonstrate that inhibiting P-gp enhances the chemotherapeutic activity of OA.

Does modulation of organic cation transporters improve pralidoxime activity in an animal model of organophosphate poisoning?

OBJECTIVES: Pralidoxime is an organic cation used as an antidote in addition to atropine to treat organophosphate poisoning. Pralidoxime is rapidly eliminated by the renal route and thus has limited action. The objectives of this work were as follows. 1) Study the role of organic cation transporters in the renal secretion of pralidoxime using organic cation transporter substrates (tetraethylammonium) and knockout mice (Oct1/2⁻/⁻; Oct3⁻/⁻). 2) Assess whether sustained high plasma concentrations increase pralidoxime antidotal activity toward paraoxon-induced respiratory toxicity. SETTING: INSERM U705, Faculté de Pharmacie, Université Paris Descartes, 4 Avenue de l'Observatoire, 75006 Paris, France. SUBJECTS: Rodents: Knockout mice (Oct1/2⁻/⁻; Oct3⁻/⁻) and Sprague-Dawley rats. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In rats, the renal clearance of pralidoxime was 3.6-fold higher than the creatinine clearance. Pretreatment with tetraethylammonium (75 mg/kg) in rats or deficiencies in organic cation transporters 1 and 2 in mice (Oct1/2⁻/⁻) resulted in a significant increase in plasma pralidoxime concentrations. Lack of Oct3 did not alter plasma pralidoxime concentrations. The antidotal activity of pralidoxime (50 mg/kg intramuscularly) was longer and with greater effect, resulting in a return to normal values when administered to rats pretreated with tetraethylammonium. CONCLUSIONS: Pralidoxime is secreted in rats and mice by renal Oct1 and/or Oct2 but not by Oct3. Modulation of organic cation transporter activity increased the plasma pralidoxime concentrations and the antidotal effect of pralidoxime with sustained return within the normal range of respiratory variables in paraoxon-poisoned rats. These results suggest a promising approach in an animal model toward the increase in efficiency of pralidoxime. However, further studies are needed before these results are extended to human poisoning.

Acute renal failure enhances the antidotal activity of pralidoxime towards paraoxon-induced respiratory toxicity.

We recently showed in a rat model of dichromate-induced acute renal failure (ARF) that the elimination but not the distribution of pralidoxime was altered resulting in sustained plasma pralidoxime concentrations. The aim of this study was to compare the efficiency of pralidoxime in normal and acute renal failure rats against paraoxon-induced respiratory toxicity. Ventilation at rest was assessed using whole-body plethysmography after subcutaneous administration of either saline or paraoxon (50% of the LD(50)), in the control and ARF rats. Thirty minutes after administration of paraoxon, either saline or 50mg/kg of pralidoxime was administered intramuscularly. ARF had no significant effects on the ventilation at rest. The effects of paraoxon on respiration were not significantly different in the control and ARF group. Paraoxon increased the total time (T(TOT)), expiratory time (T(E)) and tidal volume (V(T)), and decreased the respiratory frequency (f). In paraoxon-poisoned rats with normal renal function, pralidoxime had a significant but transient effect regarding the T(TOT) and V(T) (p<0.05). In the ARF group, the same dose of pralidoxime significantly decreased the T(TOT), T(E), and V(T) and increased f during 90 min (p<0.01). In conclusion, pralidoxime had partial and transient effects towards paraoxon-induced respiratory toxicity in control rats; and a complete and sustained correction in ARF rats.

Acute renal failure alters the kinetics of pralidoxime in rats.

There is a trend towards increasing doses of pralidoxime to treat human organophosphate poisonings that may have relevance in subpopulations. Indeed, pralidoxime is eliminated unchanged by the renal route. This study assesses the effect of renal failure on the kinetics of pralidoxime in a rat model of acute renal failure induced by potassium dichromate administration. On the first day, Sprague-Dawley rats received subcutaneously potassium dichromate (study) or saline (control). Forty-eight hours post-injection, animals received pralidoxime methylsulfate (50mg/kg of pralidoxime base) intramuscularly. Blood specimens were sampled during 180min after the injection. Urine was collected daily during the 3 days of the study. Plasma pralidoxime concentrations were measured by liquid chromatography with electrochemical detection. There was a 2-fold increase in mean elimination half-life and a 2.5-fold increase in mean area under the curve in the study compared to the control group. The mean total body clearance was halved in the study compared to the control group. Our study showed acute renal failure does not modify the distribution of pralidoxime but significantly alters its elimination from plasma. These results suggest that dosages of pralidoxime should be adjusted in organophosphate-poisoned humans with renal failure when using high dosage regimen of pralidoxime.

Ventilatory effects of low-dose paraoxon result from central muscarinic effects.

Paraoxon induces respiratory toxicity. Atropine completely reversed parathion- and paraoxon-induced respiratory toxicity. The aim of this study was to assess the peripheral or central origin of ventilatory effects of low-dose paraoxon. Male Sprague-Dawley rats were given paraoxon 0.215 mg/kg subcutaneously and treated with either atropine (10 mg/kg sc) or ascending doses of methylatropine of 5.42 (equimolar to that of atropine), 54.2, and 542 mg/kg administered subcutaneously 30 min after paraoxon. Ventilation at rest was assessed using whole-body plethysmography and rat temperature using infra-red telemetry. Results are expressed as mean+/-SE. Statistical analysis used two-way ANOVA for repeated measurements. Paraoxon induced a significant decrease in temperature 30 min after injection lasting the 90 min of the study period. This effect was partially corrected by atropine, but not by methylatropine whatever the dose. Paraoxon induced a decrease in respiratory rate resulting from an increase in expiratory time associated with an increase in tidal volume. Atropine completely reversed the ventilatory effects of low-dose paraoxon while the equimolar dose of methylatropine had no significant effects. The 54.2 and 542 mg/kg doses of methylatropine had no significant effects. Atropine crosses the blood-brain barrier and reverses peripheral and central muscarinic effects. In contrast, methylatropine does not cross the blood-brain barrier. Atropine completely reversed the ventilatory effects of low-dose paraoxon, while methylatropine had no significant effects at doses up to 100-fold the equimolar dose of atropine. We conclude that the ventilatory effects of low-dose paraoxon are mediated by disrupted muscarinic signaling in the central nervous system.