UNLABELLED: To evaluate the cellular permeation characteristics and the chemical and enzymatic stability of coumarinic acid-based cyclic prodrugs 1 and 2 of the opioid peptides [Leu5]-enkephalin (H-Tyr-Gly-Gly-Phe-Leu-OH) and DADLE (H-Tyr-D-Ala-Gly-Phe-D-Leu-OH), respectively. METHODS: The rates of conversion of the cyclic prodrugs 1 and 2 to [Leu5]-enkephalin and DADLE, respectively, in HBSS, pH 7.4 (Caco-2 cell transport buffer) and in various biological media having measurable esterase activity were determined by HPLC. The cell permeation characteristics of [Leu5]-enkephalin, DADLE and cyclic prodrugs 1 and 2 were measured using Caco-2 cell monolayers grown onto microporus membranes and monitored by HPLC. RESULTS: In HBSS, pH 7.4, cyclic prodrugs 1 and 2 degraded chemically to intermediates that further degraded to [Leu5]-enkephalin and DADLE, respectively, in stoichiometric amounts. In 90% human plasma and rat liver homogenate, the disappearance of cyclic prodrugs 1 and 2 was significantly faster than in HBSS, pH 7.4. The half-lives in 90% human plasma and in rat liver homogenate were substantially longer after pretreatment with paraoxon, a known inhibitor of serine-dependent esterases. When applied to the AP side of a Caco-2 cell monolayer, cyclic prodrug 1 exhibited significantly greater stability against peptidase metabolism than did [Leu5]-enkephalin. Cyclic prodrug 2 and DADLE exhibited similar stability when applied to the AP side of the Caco-2 cell monolayer. Prodrug 1 was 665-fold more able to permeate the Caco-2 cell monolayers than was [Leu5]-enkephalin, in part because of its increased enzymatic stability. Prodrug 2 was shown to be approximately 31 fold more able to permeate a Caco-2 cell monolayer than was DADLE. CONCLUSIONS: Cyclic prodrugs 1 and 2, prepared with the coumarinic acid promoiety, were substantially more able to permeate Caco-2 cell monolayers than were the corresponding opioid peptides. Prodrug 1 exhibited increased stability to peptidase metabolism compared to [Leu5]-enkephalin. In various biological media, the opioid peptides were released from the prodrugs by an esterase-catalyzed reaction, which is sensitive to paraoxon inhibition.
UNLABELLED: To evaluate the cellular permeation characteristics and the chemical and enzymatic stability of coumarinic acid-based cyclic prodrugs 1 and 2 of the opioid peptides [Leu5]-enkephalin (H-Tyr-Gly-Gly-Phe-Leu-OH) and DADLE (H-Tyr-D-Ala-Gly-Phe-D-Leu-OH), respectively. METHODS: The rates of conversion of the cyclic prodrugs 1 and 2 to [Leu5]-enkephalin and DADLE, respectively, in HBSS, pH 7.4 (Caco-2 cell transport buffer) and in various biological media having measurable esterase activity were determined by HPLC. The cell permeation characteristics of [Leu5]-enkephalin, DADLE and cyclic prodrugs 1 and 2 were measured using Caco-2 cell monolayers grown onto microporus membranes and monitored by HPLC. RESULTS: In HBSS, pH 7.4, cyclic prodrugs 1 and 2 degraded chemically to intermediates that further degraded to [Leu5]-enkephalin and DADLE, respectively, in stoichiometric amounts. In 90% human plasma and rat liver homogenate, the disappearance of cyclic prodrugs 1 and 2 was significantly faster than in HBSS, pH 7.4. The half-lives in 90% human plasma and in rat liver homogenate were substantially longer after pretreatment with paraoxon, a known inhibitor of serine-dependent esterases. When applied to the AP side of a Caco-2 cell monolayer, cyclic prodrug 1 exhibited significantly greater stability against peptidase metabolism than did [Leu5]-enkephalin. Cyclic prodrug 2 and DADLE exhibited similar stability when applied to the AP side of the Caco-2 cell monolayer. Prodrug 1 was 665-fold more able to permeate the Caco-2 cell monolayers than was [Leu5]-enkephalin, in part because of its increased enzymatic stability. Prodrug 2 was shown to be approximately 31 fold more able to permeate a Caco-2 cell monolayer than was DADLE. CONCLUSIONS: Cyclic prodrugs 1 and 2, prepared with the coumarinic acid promoiety, were substantially more able to permeate Caco-2 cell monolayers than were the corresponding opioid peptides. Prodrug 1 exhibited increased stability to peptidase metabolism compared to [Leu5]-enkephalin. In various biological media, the opioid peptides were released from the prodrugs by an esterase-catalyzed reaction, which is sensitive to paraoxon inhibition.
Authors: David E Hacker; Jan Hoinka; Emil S Iqbal; Teresa M Przytycka; Matthew C T Hartman Journal: ACS Chem Biol Date: 2017-02-01 Impact factor: 5.100
Authors: Luisa L Scott; Sangeetha Iyer; Ashley E Philpo; Melva N Avalos; Natalie S Wu; Ted Shi; Brooke A Prakash; Thanh-Tu Nguyen; S John Mihic; Richard W Aldrich; Jonathan T Pierce Journal: J Pharmacol Exp Ther Date: 2018-08-29 Impact factor: 4.030