Metabolic Activation of Fluoropyrrolidine Dipeptidyl Peptidase-IV Inhibitors by Rat Liver Microsomes

Abstract The current study evaluated the potential for two dipeptidyl peptidase-IV (DPP-IV) inhibitor analogues (MRL-A and MRL-B), containing a fluoropyrrolidine moiety in the structure, to undergo metabolic activation. The irreversible binding of these tritiumlabeled compounds to rat liver microsomal protein was time-and NADPH-dependent, and was attenuated by the addition of reduced glutathione (GSH) or N-acetylcysteine (NAC) to the incubation, indicating that chemically reactive intermediates were formed and trapped by these nucleophiles. Mass spectrometric analyses and further trapping experiments with semicarbazide indicated that the fluoropyrrolidine ring had undergone sequential oxidation and defluorination events resulting in the formation of GSH or NAC conjugates of the pyrrolidine moiety. The bioactivation of MRL-A was catalyzed primarily by rat recombinant cytochrome (CYP) 3A1 and 3A2. Pretreatment of rats with prototypic CYP3A1 and 3A2 inducers (pregnenolone-16alpha-carbonitrile (PCN) and dexamethasone) enhanced the extent of bioactivation, which in turn, led to a higher degree of in vitro irreversible binding to microsomal proteins (5-and 9-fold increase, respectively). Herein, we describe studies which demonstrate that the fluoropyrrolidine ring is prone to metabolic activation, and that GSH or NAC can trap the reactive intermediates to form adducts that provide insight into the mechanisms of bioactivation

Exploring passenger assessments of bus service quality using Bayesian networks

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Heat shock protein 72 overexpression prevents early postoperative memory decline after orthopedic surgery under general anesthesia in mice. Anesthesiology

ABSTRACT Background: Problems with learning and memory are common after surgery in the elderly and are associated with high morbidity. Heat shock protein 72 (Hsp72) confers neuroprotection against acute neurologic injury. We hypothesized that overexpression of Hsp72 would prevent the development of postoperative memory loss. Methods: C57BL/6 wild-type and Hsp72 overexpressing transgenic mice were randomly allocated to the following: control, isoflurane anesthesia alone, or tibial fracture during isoflurane anesthesia. Animals were trained 24 h before surgery using a fear conditioning protocol and assessed in their training environment and in a novel context on posttreatment days 1, 3, and 7. Microglial activation was assessed by immunostaining. Results: Adult male C57BL/6 wild-type mice exhibite