Enhanced Methamphetamine Metabolism in Rhesus Macaque as Compared with Human: An Analysis Using a Novel Method of Liquid Chromatography with Tandem Mass Spectrometry, Kinetic Study, and Substrate Docking

Abstract

Methamphetamine (MA), which remains one of the widely used drugs of abuse, is metabolized by the cytochrome P450 (P450) family of enzymes in humans. However, metabolism of methamphetamine in macaques is poorly understood. Therefore, we first developed and validated a very sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) method using solid phase extraction of rhesus plasma with a lower limit of quantitation at 1.09 ng/ml for MA and its metabolites, 4-hydroxy methamphetamine (4-OH MA), amphetamine (AM), 4-OH amphetamine (4-OH AM), and norephedrine. We then analyzed plasma samples of MA-treated rhesus, which showed >10-fold higher concentrations of AM (∼29 ng/ml) and 4-OH AM (∼28 ng/ml) than MA (∼2 ng/ml). Because the plasma levels of MA metabolites in rhesus were much higher than in human samples, we examined MA metabolism in human and rhesus microsomes. Interestingly, the results showed that AM and 4-OH AM were formed more rapidly and that the catalytic efficiency (V max /K m ) for the formation of AM was ∼8-fold higher in rhesus than in human microsomes. We further examined the differences in these kinetic characteristics using three selective inhibitors of each human CYP2D6 and CYP3A4 enzymes. The results showed that each of these inhibitors inhibited both D-and L-MA metabolism by 20%-60% in human microsomes but not in rhesus microsomes. The differences between human and rhesus CYP2D6 and CYP3A4 enzymes were further assessed by docking studies for both d and l-MA. In conclusion, our results demonstrated an enhanced MA metabolism in rhesus compared with humans, which is likely to be caused by differences in MA-metabolizing P450 enzymes between these species.

Diallyl Sulfide: Potential Use in Novel Therapeutic Interventions in Alcohol, Drugs, and Disease Mediated Cellular Toxicity by Targeting Cytochrome P450 2E1

“…The most appropriate structure will be selected by comparing the size, shape, and geometry of DAS with the ligands that have been complexed with CYP2E1. Further, DAS analogs will be docked in to the active site of CYP2E1 using manual and/or auto docking methods [173]. In the case of manual docking, a particular atom of DAS analogs will be fixed with the heme of CYP2E1 and energy minimization will be carried out upon fixing the parameters that allow free movement of enzyme-ligand complex within 10Å of the heme.…”

Drug–drug interactions between anti-retroviral therapies and drugs of abuse in HIV systems

“…For example, it increases the binding of type II PIs, ritonavir, whereas it decreases/has no effects on the binding of other PIs suggesting that methamphetamine is likely to alter the metabolism of PIs in differential manner. The need for relevant clinical evaluation of methamphetamine-induced drug–drug interactions with ART is strengthened by recent report of enhanced methamphetamine metabolism in the non-human animal model of Rhesus Macaque [83]. Hence, further studies are essential to examine the role of methamphetamine on the metabolism and efficacy of ART drugs, especially PIs, which would ultimately help develop a better treatment strategy for HIV-infected methamphetamine users.…”

Impact of methamphetamine on infection and immunity

“…In this regard, some studies support that injection of METH in ranges of 3.6–10 mg/Kg are considered lethal in animals (Hendrickson et al, 2008 ). Similarly, a recent study showed an 8-fold higher catalytic activity of METH in rhesus macaques compared to humans due to enzymatic differences (Earla et al, 2014 ).…”