PD 102807 Induces M3 mAChR-Dependent GRK-/Arrestin-Biased Signaling in Airway Smooth Muscle Cells.

G protein-coupled receptors (GPCRs) not only are turned on or off to control canonical G protein signaling but also may be fine-tuned to promote qualitative/biased signaling. Qualitative signaling by M3 muscarinic acetylcholine receptors (mAChRs) has been proposed, but its impact on physiologic systems remains unclear, and currently no biased M3 mAChR ligands have been described. Herein, we identify PD 102807 as a biased M3 ligand and delineate its signaling and function in human airway smooth muscle (ASM) cells. PD 102807 induced M3-mediated ß-arrestin recruitment but not calcium mobilization. PD 102807 inhibited methacholine (MCh)-induced calcium mobilization in (M3-expressing) ASM cells. PD 102807 induced phosphorylation of AMP-activated protein kinase (AMPK) and the downstream effector acetyl-coenzyme A carboxylase (ACC). PD 102807- induced phosphorylated (p)-AMPK levels were greatly reduced in ASM cells with minimal M3 expression and were not inhibited by the Gq inhibitor YM-254890. Induction of p-AMPK and p-ACC was inhibited by ß-arrestin 1 or GRK2/3 knockdown. Similarly, MCh induced phosphorylation of AMPK/ACC, but these effects were Gq dependent and unaffected by GRK2/3 knockdown. Consistent with the known ability of AMPK to inhibit transforming growth factor ß (TGF-ß)-mediated functions, PD 102807 inhibited TGF-ß-induced SMAD-Luc activity, sm-α-actin expression, actin stress fiber formation, and ASM cell hypercontractility. These findings reveal that PD 102807 is a biased M3 ligand that inhibits M3-transduced Gq signaling but promotes Gq protein-independent, GRK-/arrestin-dependent, M3-mediated AMPK signaling, which in turn regulates ASM phenotype and contractile function. Consequently, biased M3 ligands hold significant promise as therapeutic agents capable of exploiting the pleiotropic nature of M3 signaling.

Adolescent d-amphetamine exposure enhances the acquisition of cocaine self-administration in male and female rats.

Diagnosis and treatment of attention-deficit/hyperactivity disorder (ADHD) has risen drastically over the past 20 years in the United States and abroad. Amphetamine-based prescription stimulants are the most prescribed treatment for ADHD and the diversion of these drugs has also increased. Reports indicate 61% of individuals with an ADHD medication prescription have sold or shared their medication. Exposure to prescription stimulants, especially for those without an ADHD diagnosis, may increase susceptibility to drugs of abuse. The present study aimed to model ADHD medication misuse during adolescence in male and female rats. The primary dependent measure was the acquisition of intravenous cocaine self-administration. Male and female, Long-Evans rats were exposed to d-amphetamine (0.7 mg/kg, i.p.) or saline in adolescence (35-41 days old), during which locomotor activity was measured. At approximately 75 days old, animals were implanted with jugular catheters. All animals then entered a 15-day acquisition procedure with no prior operant training. Finally, following acquisition all animals responded on a progressive-ratio (PR) schedule to obtain 0, 0.1, 0.3, and 1.0 mg/kg/infusion cocaine. Animals exposed to amphetamine acquired cocaine self-administration faster than saline-exposed controls when the acquisition criterion was operationally defined as two consecutive days with 12 infusions or greater. Discrete-time hazard modeling also found amphetamine exposure to increase the likelihood of acquiring cocaine self-administration. There were no differences detected during PR testing. These data suggest that individuals with histories of prescription stimulant misuse may be at increased risk to use other drugs of abuse. (PsycINFO Database Record