Zhx2 Is a Candidate Gene Underlying Oxymorphone Metabolite Brain Concentration Associated with State-Dependent Oxycodone Reward.

Understanding the pharmacogenomics of opioid metabolism and behavior is vital to therapeutic success, as mutations can dramatically alter therapeutic efficacy and addiction liability. We found robust, sex-dependent BALB/c substrain differences in oxycodone behaviors and whole brain concentration of oxycodone metabolites. BALB/cJ females showed robust state-dependent oxycodone reward learning as measured via conditioned place preference when compared with the closely related BALB/cByJ substrain. Accordingly, BALB/cJ females also showed a robust increase in brain concentration of the inactive metabolite noroxycodone and the active metabolite oxymorphone compared with BALB/cByJ mice. Oxymorphone is a highly potent, full agonist at the mu opioid receptor that could enhance drug-induced interoception and state-dependent oxycodone reward learning. Quantitative trait locus (QTL) mapping in a BALB/c F2 reduced complexity cross revealed one major QTL on chromosome 15 underlying brain oxymorphone concentration that explained 32% of the female variance. BALB/cJ and BALB/cByJ differ by fewer than 10,000 variants, which can greatly facilitate candidate gene/variant identification. Hippocampal and striatal cis-expression QTL (eQTL) and exon-level eQTL analysis identified Zhx2, a candidate gene coding for a transcriptional repressor with a private BALB/cJ retroviral insertion that reduces Zhx2 expression and sex-dependent dysregulation of cytochrome P450 enzymes. Whole brain proteomics corroborated the Zhx2 eQTL and identified upregulated CYP2D11 that could increase brain oxymorphone in BALB/cJ females. To summarize, Zhx2 is a highly promising candidate gene underlying brain oxycodone metabolite levels. Future studies will validate Zhx2 and its site of action using reciprocal gene editing and tissue-specific viral manipulations in BALB/c substrains. SIGNIFICANCE STATEMENT: Our findings show that genetic variation can result in sex-specific alterations in whole brain concentration of a bioactive opioid metabolite after oxycodone administration, reinforcing the need for sex as a biological factor in pharmacogenomic studies. The cooccurrence of female-specific increased oxymorphone and state-dependent reward learning suggests that this minor yet potent and efficacious metabolite of oxycodone could increase opioid interoception and drug-cue associative learning of opioid reward, which has implications for cue-induced relapse of drug-seeking behavior and for precision pharmacogenetics.

Clinical pharmacokinetics of atropine oral gel formulation in healthy volunteers.

Sialorrhea or drooling is a common problem in children and adults with neurodevelopmental disorders. It can negatively impact the quality of life due to its physical and psychological manifestations. Providers commonly prescribe atropine eye drops for topical administration to the oral mucosa, as an off-label treatment to manage sialorrhea. However, the off-label use of atropine eye drops can be associated with medication and dosing errors and systemic side effects. To address these limitations of treatment, we developed a mucoadhesive topical oral gel formulation of atropine as an alternative route to off-label administration of atropine eye drops. In this clinical pharmacokinetic (PK) study, we evaluated the safety and PK of atropine gel (0.01% w/w) formulation after single-dose administration to the oral mucosa in 10 healthy volunteers. The PK data showed that after topical administration to the oral mucosa, atropine followed a two-compartment PK profile. The maximum plasma concentration and area under the curve extrapolated to infinite time were 0.14 ng/mL and 0.74 h·ng·mL-1 , respectively. The absorption rate constant calculated by the compartmental analysis was 0.4 h-1 . Safety parameters, such as heart rate, blood pressure, and oxygen saturation, did not significantly change before and after administration of the gel formulation, and no adverse events were observed in all participants who received atropine gel. These data indicate that atropine gel formulation has a satisfactory PK profile, is well-tolerated at the dose studied, and can be further considered for clinical development as a drug product to treat sialorrhea.

Validation studies and multi-omics analysis of Zhx2 as a candidate quantitative trait gene underlying brain oxycodone metabolite (oxymorphone) levels and behavior.

Sensitivity to the subjective reinforcing properties of opioids has a genetic component and can predict addiction liability of opioid compounds. We previously identified Zhx2 as a candidate gene underlying increased brain concentration of the oxycodone (OXY) metabolite oxymorphone (OMOR) in BALB/cJ (J) versus BALB/cByJ (By) females that could increase OXY state-dependent reward. A large structural intronic variant is associated with a robust reduction of Zhx2 expression in J mice, which we hypothesized enhances OMOR levels and OXY addiction-like behaviors. We tested this hypothesis by restoring the Zhx2 loss-of-function in Js (MVKO) and modeling the loss-of-function variant through knocking out the Zhx2 coding exon (E3KO) in Bys and assessing brain OXY metabolite levels and behavior. Consistent with our hypothesis, Zhx2 E3KO females showed an increase in brain OMOR levels and OXY-induced locomotor activity. However, contrary to our hypothesis, state-dependent expression of OXY-CPP was decreased in E3KO females and increased in E3KO males. We also overexpressed Zhx2 in the livers and brains of Js and observed Zhx2 overexpression in select brain regions that was associated with reduced OXY state-dependent learning. Integrative transcriptomic and proteomic analysis of E3KO mice identified astrocyte function, cell adhesion, extracellular matrix properties, and endothelial cell functions as pathways influencing brain OXY metabolite concentration and behavior. These results support Zhx2 as a quantitative trait gene underlying brain OMOR concentration that is associated with changes in OXY behavior and implicate potential quantitative trait mechanisms that together inform our overall understanding of Zhx2 in brain function.

Pharmacokinetics of Single-Dose Intramuscular and Subcutaneous Injections of Buprenorphine in Common Marmosets (Callithrix jacchus).

Although buprenorphine is the most frequently used opioid analgesic in common marmosets (Callithrix jacchus), there is limited information in the literature supporting current dosing regimens used for this species. The purpose of this study was to determine the pharmacokinetic profiles of single-dose buprenorphine HCl administered intramuscularly (IM) at 0.01 mg/kg in 6 adult marmosets (1.8 to 12.8 y old; 2 males, 4 females) and subcutaneously (SQ) at 0.01 mg/kg in 6 adult marmo- sets (2.3-4.4 y old; 3 males, 3 females) by mass spectrometry. Blood was collected at multiple time points from 0.25 to 24 h from unsedated animals following a hybrid sparse-serial sampling design. The maximal observed plasma concentration of buprenorphine (Cmax ) administered IM (2.57 ± 0.95 ng/mL) was significantly higher than administered SQ (1.47 ± 0.61 ng/mL). However, the time to Cmax (Tmax) was not statistically different between routes (17.4 ± 6 min for IM and 19.8 ± 7.8 min for SQ). The time of the last quantifiable concentration of buprenorphine was 5 ± 1.67 h for IM compared with 6.33 ± 1.51 h for SQ, which was not statistically different. The mean buprenorphine plasma concentration-time curves were used to propose a dosing frequency of 4 to 6 h for buprenorphine at 0.01 mg/kg IM or SQ based on a theoretical therapeutic plasma concentration threshold of 0.1 ng/mL. Based on the mean pharmacokinetic parameters and plasma-concentration time curves, both IM and SQ routes of buprenorphine at this dose provide a rapid increase in the plasma concentration of buprenorphine above the therapeutic threshold, and may be more effective for acute rather than long-lasting analgesia. Further studies are needed to examine repeated dosing regimens and the efficacy of buprenorphine in common marmosets.

Buprenorphine and norbuprenorphine in hair of pregnant women and their infants after controlled buprenorphine administration.

BACKGROUND: Buprenorphine is under investigation as a pharmacotherapeutic agent for treating opioid dependence in pregnant women. We hypothesized that there would be a relationship between the cumulative maternal dose of buprenorphine during pregnancy and the concentration of buprenorphine and norbuprenorphine in maternal and infant hair. METHODS: This study examined buprenorphine and norbuprenorphine concentrations in hair obtained from 9 buprenorphine-maintained pregnant women and 4 of their infants. Specimens were analyzed by liquid chromatography-tandem mass spectrometry with limits of quantification of 3.0 pg/mg. All maternal hair specimens were washed with methylene chloride before analysis, and when sufficient amounts of maternal hair were available, specimens also were analyzed without washing. Infant hair specimens were not washed. RESULTS: Buprenorphine concentrations were significantly greater in unwashed hair than washed hair (P = 0.031). Norbuprenorphine concentrations were significantly greater than buprenorphine concentrations in both maternal (P = 0.0097) and infant hair (P = 0.0033). There were statistically significant associations between the cumulative maternal dose of buprenorphine administered and the concentrations of buprenorphine (washed, P <0.0001; unwashed, P = 0.0004), norbuprenorphine (washed, P <0.0001; unwashed, P = 0.0005), and buprenorphine plus norbuprenorphine (washed, P <0.0001; unwashed, P = 0.0005) for both washed and unwashed maternal hair specimens. There was a significant positive association between concentrations of buprenorphine and norbuprenorphine in maternal hair (washed, P <0.0001; unwashed, P = 0.0003), a trend for this association in infant hair (P = 0.08), and an association between buprenorphine concentrations in maternal unwashed hair and infant hair (P = 0.0002). The buprenorphine:norbuprenorphine ratio increased in distal segments. CONCLUSION: Buprenorphine treatment during gestation provides an opportunity for monitoring drug disposition in maternal and fetal tissues under controlled conditions.

Biomimetic studies on the mechanism of stereoselective lanthionine formation.

Selenocysteine derivatives are useful precursors for the synthesis of peptide conjugates and selenopeptides. Several diastereomers of Fmoc-3-methyl-Se-phenylselenocysteine (FmocMeSec(Ph)) were prepared and used in solid phase peptide synthesis (SPPS). Once incorporated into peptides, the phenylselenide functionality provides a useful handle for the site and stereospecific introduction of E- or Z-dehydrobutyrine residues into peptide chains via oxidative elimination. The oxidation conditions are mild, can be performed on a solid support, and tolerate functionalities commonly found in peptides, including variously protected cysteine residues. Dehydropeptides containing unprotected cysteine residues undergo intramolecular stereoselective conjugate addition to afford cyclic lanthionines and methyllanthionines, which have the same stereochemistry as found in lantibiotics, a family of ribosomally synthesized and post-translationally modified peptide antibiotics. The observed stereoselectivity is shown to originate from a kinetic rather than a thermodynamic preference.

Lacticin 481: in vitro reconstitution of lantibiotic synthetase activity.

The lantibiotic lacticin 481 is synthesized on ribosomes as a prepeptide (LctA) and posttranslationally modified to its mature form. These modifications include dehydration of serines and threonines, followed by intramolecular addition of cysteines to the unsaturated amino acids, which generates cyclic thioethers. This process breaks eight chemical bonds and forms six newbonds and is catalyzed by one enzyme, LctM. We have characterized the in vitro activity of LctM, which completely processed a series of LctA mutants, displaying a permissive substrate specificity that holds promise for antibiotic engineering.