Biology subjects

Streicher, J. M.

Publications and source records attributed to Streicher, J. M..

6 recordsLinked to original sources

bioRxiv2026

Discovery and dynamic pharmacology of μ-opioid receptor positive allosteric modulators

Opioid agonists such as morphine and fentanyl exert analgesic effects by binding and activating the {micro}-opioid receptor ({micro}OR), yet agonism of the {micro}OR causes a slate of serious side effects. {micro}OR-mediated addiction and respiratory depression are the major causes of the current opioid overdose crisis, largely driven by the explosion in illicit use of fentanyl, a potent opioid receptor full agonist. Given these serious side effects (and high resulting societal cost), molecules that act as analgesics with distinct mechanisms of action are of great interest. Positive allosteric modulators (PAMs) of the {micro}OR have the potential to avoid many off-target side effects of conventional opioid orthosteric agonists by enhancing the signaling properties of natural opioid peptide systems. We used a DNA-encoded chemical library screening approach to selectively discover active-state-specific {micro}OR PAMs. Two out of 3 selected prospective PAMs displayed the anticipated enhancement in agonist activity. The most effective of these compounds enhanced the activity of all orthosteric opioid agonists tested, including the native opioid peptide met-enkephalin. Little is known about the underlying dynamic basis of allosteric modulation of Family A GPCRs like the {micro}OR. To that end, we used single-molecule fluorescence resonance energy transfer experiments to detail the impact that our novel {micro}OR PAM has on the dynamic activation behavior of a key region on the intracellular face of the receptor. Our results here provide both a new chemical scaffold that acts as a {micro}OR PAM and detailed pharmacological and dynamic insights into its mechanism of action.

biophysics↗

bioRxiv2023

The Role of Ryanodine Receptor 2 in Drug-Associated Learning

Type-2 ryanodine receptor (RyR2) ion channels facilitate the release of Ca2+ from stores and serve an important function in neuroplasticity. The role for RyR2 in hippocampal-dependent learning and memory is well established and chronic hyperphosphorylation of RyR2 (RyR2P) is associated with pathological calcium leakage and cognitive disorders, including Alzheimers disease. By comparison, little is known about the role of RyR2 in the ventral medial prefrontal cortex (vmPFC) circuitry important for working memory, decision making, and reward seeking. Here, we evaluated the basal expression and localization of RyR2 and RyR2P in the vmPFC. Next, we employed an operant model of sucrose, cocaine, or morphine self-administration (SA) followed by a (reward-free) recall test, to reengage vmPFC neurons and reactivate reward-seeking and re-evaluated the expression and localization of RyR2 and RyR2P in vmPFC. Under basal conditions, RyR2 was expressed in pyramidal cells but not regularly detected in PV/SST interneurons. On the contrary, RyR2P was rarely observed in PFC somata and was restricted to a different subcompartment of the same neuron - the apical dendrites of layer-5 pyramidal cells. Chronic SA of drug (cocaine or morphine) and nondrug (sucrose) rewards produced comparable increases in RyR2 protein expression. However, recalling either drug reward impaired the usual localization of RyR2P in dendrites and markedly increased its expression in somata immunoreactive for Fos, a marker of highly activated neurons. These effects could not be explained by chronic stress or drug withdrawal and instead appeared to require a recall experience associated with prior drug SA. In addition to showing the differential distribution of RyR2/RyR2P and affirming the general role of vmPFC in reward learning, this study provides information on the propensity of addictive drugs to redistribute RyR2P ion channels in a neuronal population engaged in drug-seeking. Hence, focusing on the early impact of addictive drugs on RyR2 function may serve as a promising approach to finding a treatment for substance use disorders.

neuroscience↗

bioRxiv2023

Terpenes from Cannabis sativa Induce Antinociception in Mouse Chronic Neuropathic Pain via Activation of Spinal Cord Adenosine A2A Receptors

Terpenes are small hydrocarbon compounds that impart aroma and taste to many plants, including Cannabis sativa. A number of studies have shown that terpenes can produce pain relief in various pain states in both humans and animals. However, these studies were methodologically limited and few established mechanisms of action. In our previous work, we showed that the terpenes geraniol, linalool, {beta}-pinene, - humulene, and {beta}-caryophyllene produced cannabimimetic behavioral effects via multiple receptor targets. We thus expanded this work to explore the efficacy and mechanism of these Cannabis terpenes in relieving chronic pain. We first tested for antinociceptive efficacy by injecting terpenes (200 mg/kg, IP) into male and female CD- 1 mice with chemotherapy-induced peripheral neuropathy (CIPN) or lipopolysaccharide-induced inflammatory pain, finding that the terpenes produced roughly equal efficacy to 10 mg/kg morphine or 3.2 mg/kg WIN55,212. We further found that none of the terpenes produced reward as measured by conditioned place preference, while low doses of terpene (100 mg/kg) combined with morphine (3.2 mg/kg) produced enhanced antinociception vs. either alone. We then used the adenosine A2A receptor (A2AR) selective antagonist istradefylline (3.2 mg/kg, IP) and spinal cord-specific CRISPR knockdown of the A2AR to identify this receptor as the mechanism for terpene antinociception in CIPN. In vitro cAMP and binding studies and in silico modeling studies further suggested that the terpenes act as A2AR agonists. Together these studies identify Cannabis terpenes as potential therapeutics for chronic neuropathic pain, and identify a receptor mechanism in the spinal cord for this activity.

neuroscience↗

bioRxiv2021

Inhibition of Heat Shock Protein 90 in the Spinal Cord Improves the Therapeutic Index of Morphine

Opioid drugs like morphine are the gold standard for the treatment of chronic pain, but are limited by adverse side effects, such as tolerance, constipation, and reward/addiction. In our earlier work, we showed that Heat shock protein 90 (Hsp90) has a crucial role in regulating opioid signaling that differs between brain and spinal cord; Hsp90 inhibition in brain blocks opioid pain relief, while inhibition in the spinal cord enhances it. Building on these findings here, we injected the non-selective Hsp90 inhibitor KU-32 directly into the spinal cord of male and female CD-1 mice, showing that morphine anti-nociceptive potency was boosted by 1.9-3.5 fold in the pain models of tail flick, post-surgical paw incision, and HIV peripheral neuropathy. At the same time, morphine tolerance was reduced from 21 fold to 2.9 fold and established tolerance was rescued, while the potency of constipation and reward (as measured by conditioned place preference) was unchanged. These results demonstrate that spinal Hsp90 inhibition can improve the therapeutic index of morphine. However, we also found that systemic non-selective Hsp90 inhibition resulted in a brain-like effect, blocking opioid pain relief. We thus sought a way to circumvent the effects of brain Hsp90 inhibition by investigating the molecular Hsp90 isoforms active in regulating opioid signaling in both regions. Using selective small molecule inhibitors and CRISPR gene editing, we found that 3 Hsp90 isoforms regulated spinal cord opioid signaling (Hsp90, Hsp90{beta}, and Grp94) while our previous work showed only Hsp90 was active in brain. We thus hypothesized that a systemically delivered selective inhibitor to Hsp90{beta} or Grp94 could selectively inhibit spinal cord Hsp90 activity, resulting in enhanced opioid pain relief and decreased side effects. We tested this hypothesis using intravenous delivery of KUNB106 (Hsp90{beta}) and KUNG65 (Grp94), showing that both drugs enhanced morphine potency in tail flick and paw incision pain while rescuing anti-nociceptive tolerance. We also found that intravenous KUNA115 (Hsp90) fully blocked morphine anti-nociception. Together, these results suggest that selective inhibition of spinal cord Hsp90 isoforms is a novel, translationally feasible strategy to improve the therapeutic index of opioids.

neuroscience↗

bioRxiv2020

Cannabis sativa Terpenes are Cannabimimetic and Provide Support for the Entourage Effect Hypothesis

Limited evidence has suggested that terpenes found in Cannabis sativa are analgesic, and could produce an "entourage effect" whereby they modulate cannabinoids to result in improved outcomes. However this hypothesis is controversial, with limited evidence. We thus investigated Cannabis sativa terpenes alone and with the cannabinoid agonist WIN55,212 using in vitro and in vivo approaches. We found that the terpenes -humulene, geraniol, linalool, and {beta}-pinene produced cannabinoid tetrad behaviors in mice, suggesting cannabimimetic activity. Some behaviors could be blocked by cannabinoid or adenosine receptor antagonists, suggesting a mixed mechanism of action. These behavioral effects were additive with WIN55,212, providing support for a terpene "entourage effect." In vitro experiments showed that all terpenes activated the CB1R, while some activated other targets. Our findings suggest that these Cannabis terpenes are multifunctional cannabimimetic ligands that provide support for the entourage effect hypothesis and could be used to enhance the therapeutic properties of cannabinoids.

pharmacology and toxicology↗

bioRxiv2018

Targeting the CaV - interaction yields a selective antagonist of the N-type CaV2.2 channel with broad antinociceptive efficacy

Inhibition of voltage-gated calcium (CaV) channels is a potential therapy for many neurological diseases including chronic pain. Neuronal CaV1/CaV2 channels are composed of , {beta} and 2{delta} subunits. The {beta}-subunits of CaV channels are cytoplasmic proteins that increase the surface expression of the pore-forming subunit of CaV. We targeted the high-affinity protein-protein interface of CaV{beta}s pocket within the CaV-subunit. Structure-based virtual screening of 50,000 small molecule library docked to the {beta}-subunit led to the identification of 2-(3,5-dimethylisoxazol-4-yl)-N-((4-((3-phenylpropyl)amino)quinazolin-2-yl)methyl)acetamide (compound 45). This small molecule bound to CaV{beta} and inhibited its coupling with N-type voltage-gated calcium (CaV2.2) channels, leading to a reduction in CaV2.2 currents in rat dorsal root ganglion (DRG) sensory neurons, decreased pre-synaptic localization of CaV2.2 in vivo, decreased frequency of spontaneous excitatory post-synaptic potentials (sEPSC), and inhibited release of the nociceptive neurotransmitter calcitonin gene related peptide (CGRP) from spinal cord. 45 was antinociceptive in naive animals and reversed allodynia and hyperalgesia in models of acute (post-surgical) and neuropathic (spinal nerve ligation, chemotherapy- and gp120-induced peripheral neuropathy, and genome-edited neuropathy) pain. 45 did not cause akinesia or motor impairment, a common adverse effect of CaV2.2 targeting drugs, when injected into the brain. 45, a quinazoline analog, represents a novel class of CaV2.2-targeting compounds that may serve as probes to interrogate CaV-{beta} function and ultimately be developed as a non-opioid therapeutic for chronic pain.

neuroscience↗