Dual Piperidine-Based Histamine H3 and Sigma-1 Receptor Ligands in the Treatment of Nociceptive and Neuropathic Pain

In search of new dual-acting histamine H3/sigma-1 receptor ligands, we designed a series of compounds structurally based on highly active in vivo ligands previously studied and described by our team. However, we kept in mind that within the previous series, a pair of closely related compounds, KSK67 and KSK68, differing only in the piperazine/piperidine moiety in the structural core showed a significantly different affinity at sigma-1 receptors (σ1Rs). Therefore, we first focused on an in-depth analysis of the protonation states of piperazine and piperidine derivatives in the studied compounds. In a series of 16 new ligands, mainly based on the piperidine core, we selected three lead structures (3, 7, and 12) for further biological evaluation. Compound 12 showed a broad spectrum of analgesic activity in both nociceptive and neuropathic pain models based on the novel molecular mechanism

Small Synthetic Hyaluronan Disaccharide BIS014 Mitigates Neuropathic Pain in Mice

Supplementary data Supplementary data related to this article can be found at https://doi.org/10.1016/j.jpain.2022.07.014.Neuropathic pain (NP) is a challenging condition to treat, as the need for new drugs to treat NP is an unmet goal. We investigated the analgesic potential of a new sulfated disaccharide compound, named BIS014. Oral administration (p.o.) of this compound induced ameliorative effects in formalin-induced nociception and capsaicin-induced secondary mechanical hypersensitivity in mice, but also after partial sciatic nerve transection (spared nerve injury), chemotherapy (paclitaxel)-induced NP, and diabetic neuropathy induced by streptozotocin. Importantly, BIS014, at doses active on neuropathic hypersensitivity (60 mg/kg/p.o.), did not alter exploratory activity or motor coordination (in the rotarod test), unlike a standard dose of gabapentin (40 mg/kg/p.o.) which although inducing antiallodynic effects on the NP models, it also markedly decreased exploration and motor coordination. In docking and molecular dynamic simulation studies, BIS014 interacted with TRPV1, a receptor involved in pain transmission where it behaved as a partial agonist. Additionally, similar to capsaicin, BIS014 increased cytosolic Ca2+ concentration ([Ca2+]c) in neuroblastoma cells expressing TRPV1 receptors; these elevations were blocked by ruthenium red. BIS014 did not block capsaicin-elicited [Ca2+]c transients, but inhibited the increase in the firing rate of action potentials in bradykinin-sensitized dorsal root ganglion neurons stimulated with capsaicin. Perspective: We report that the oral administration of a new sulfated disaccharide compound, named BIS014, decreases neuropathic pain from diverse etiology in mice. Unlike the comparator gabapentin, BIS014 does not induce sedation. Thus, BIS014 has the potential to become a new efficacious non-sedative oral medication for the treatment of neuropathic pain.Laboratorios Bioibérica (Barcelona)Universidad Autónoma de Madrid (UAM

Synthesis, In Vitro Profiling, and In Vivo Evaluation of Benzohomoadamantane-Based Ureas for Visceral Pain: A New Indication for Soluble Epoxide Hydrolase Inhibitors

The soluble epoxide hydrolase (sEH) has been suggested as a pharmacological target for the treatment of several diseases, including pain-related disorders. Herein, we report further medicinal chemistry around new benzohomoadamantane-based sEH inhibitors (sEHI) in order to improve the drug metabolism and pharmacokinetics properties of a previous hit. After an extensive in vitro screening cascade, molecular modeling, and in vivo pharmacokinetics studies, two candidates were evaluated in vivo in a murine model of capsaicin-induced allodynia. The two compounds showed an anti-allodynic effect in a dose-dependent manner. Moreover, the most potent compound presented robust analgesic efficacy in the cyclophosphamide-induced murine model of cystitis, a well-established model of visceral pain. Overall, these results suggest painful bladder syndrome as a new possible indication for sEHI, opening a new range of applications for them in the visceral pain field.Spanish Government SAF2017-82771-R RTI2018-093955-B-C21 PGC2018-102192-B-I00 RTI2018-101032-J-I00 Spanish MCIN/AEIERDF A way of making Europe - MCIN/AEI PID2020-118127RB-I00PID2019-106285RBERDF A way of making EuropeXunta de GaliciaEuropean Commission ED431G 2019/02ED431C 2018/21Fundacio Bosch i GimperaUniversitat de Barcelona (F2I grant) Generalitat de Catalunya 2017 SGR 106 2017 SGR 1707European Research Council (ERC) European Commission ERC-2015-StG-679001-NetMoDEzyme European Commission MSCA-IF-2014-EF661160-MetAccemblyUniversitat de Barcelona (APIF grant)Spanish Society of Medicinal Chemistry (SEQT) and Lilly FWO 12Y0720NMinistry of Science and Innovation, Spain (MICINN) Spanish Government RYC2020-029552-IUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA R35 ES03443 P42 ES004699United States Department of Health & Human Services National Institutes of Health (NIH) - USA NIH National Institute of Neurological Disorders & Stroke (NINDS) R01 DK107767 United States Department of Health & Human Services National Institutes of Health (NIH) - USA NIH National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK) R01 DK10361

Discovery of AD258 as a Sigma Receptor Ligand with Potent Antiallodynic Activity

This work was funded by Italian Minister of University and Research project PRIN 2017-201744BN5T. Grant funding (VKA): National Institutes of Health-National Eye Institute-R01EY029409, P30EY00179, National Institutes of Neurological Disorders and Stroke R01NS124784, Unrestricted Grant, Research to Prevent Blindness, New York, NY. This study was partially supported by the Spanish State Research Agency (10.13039/501100011033) under the auspices of MINECO (grant number PID2019-108691RB-I00) and the Andalusian Regional Government (grant CTS109).The design and synthesis of a series of 2,7-diazaspiro[4.4]nonanederivatives as potent sigma receptor (SR) ligands, associated withanalgesic activity, are the focus of this work. In this study, affinitiesat S1R and S2R were measured, and molecular modeling studies wereperformed to investigate the binding pose characteristics. The mostpromising compounds were subjected to in vitro toxicitytesting and subsequently screened for in vivo analgesicproperties. Compound 9d (AD258) exhibitednegligible in vitro cellular toxicity and a highbinding affinity to both SRs (K (i)S1R =3.5 nM, K (i)S2R = 2.6 nM), but not for otherpain-related targets, and exerted high potency in a model of capsaicin-inducedallodynia, reaching the maximum antiallodynic effect at very low doses(0.6-1.25 mg/kg). Functional activity experiments showed thatS1R antagonism is needed for the effects of 9d and thatit did not induce motor impairment. In addition, 9d exhibiteda favorable pharmacokinetic profile.Ministry of Education, Universities and Research (MIUR) PRIN 2017-201744BN5TUnited States Department of Health & Human Services National Institutes of Health (NIH) - USA NIH National Eye Institute (NEI) R01EY029409, P30EY00179United States Department of Health & Human Services National Institutes of Health (NIH) - USA NIH National Institute of Neurological Disorders & Stroke (NINDS) R01NS124784Unrestricted Grant, Research to Prevent Blindness, New York, NYSpanish Government PID2019-108691RB-I00Andalusian Regional Government CTS10

Calmodulin Supports TRPA1 Channel Association with Opioid Receptors and Glutamate NMDA Receptors in the Nervous Tissue

Supplementary Materials: The following are available online at https://www.mdpi.com/1422-006 7/22/1/229/s1, Figure S1: TRPA1 association with MORs in spinal cord in HINT1-/- and 1R-/- mice. Figure S2: The HINT1 protein or 1R does not support the MOR association with the Nt or Ct regions of TRPA1 channels. Figure S3: CaM mediates the TRPA1 Ct association with MOR in the absence of Ca2+. Figure S4: Pharmacological modulation of TRPA1 associations with MORs and glutamate NMDARs. Figure S5: Formalin-induced inflammatory pain alters TRPA1 associations with MORs and NMDARs. Figure S6: TRPA1 associations with opioid receptors and NMDARs in the CCI model of neuropathic pain.We would like to thank Gabriela de Alba and María José López for their excellent technical assistanceTransient receptor potential ankyrin member 1 (TRPA1) belongs to the family of thermo TRP cation channels that detect harmful temperatures, acids and numerous chemical pollutants. TRPA1 is expressed in nervous tissue, where it participates in the genesis of nociceptive signals in response to noxious stimuli and mediates mechanical hyperalgesia and allodynia associated with different neuropathies. The glutamate N-methyl-d-aspartate receptor (NMDAR), which plays a relevant role in allodynia to mechanical stimuli, is connected via histidine triad nucleotide-binding protein 1 (HINT1) and type 1 sigma receptor (σ1R) to mu-opioid receptors (MORs), which mediate the most potent pain relief. Notably, neuropathic pain causes a reduction in MOR antinociceptive efficacy, which can be reversed by blocking spinal NMDARs and TRPA1 channels. Thus, we studied whether TRPA1 channels form complexes with MORs and NMDARs that may be implicated in the aforementioned nociceptive signals. Our data suggest that TRPA1 channels functionally associate with MORs, delta opioid receptors and NMDARs in the dorsal root ganglia, the spinal cord and brain areas. These associations were altered in response to pharmacological interventions and the induction of inflammatory and also neuropathic pain. The MOR-TRPA1 and NMDAR-TRPA1 associations do not require HINT1 or σ1R but appear to be mediated by calcium-activated calmodulin. Thus, TRPA1 channels may associate with NMDARs to promote ascending acute and chronic pain signals and to control MOR antinociception.MICINN Plan Nacional I+D+i RT 2018-093677B-100University of Granada PPJIB2019.11MECD FPU 15/02356 FPU16/0321

Modulation by Sigma-1 Receptor of Morphine Analgesia and Tolerance: Nociceptive Pain, Tactile Allodynia and Grip Strength Deficits During Joint Inflammation

Sigma-1 receptor antagonism increases the effects of morphine on nociceptive pain, even in morphine-tolerant animals. However, it is unknown whether these receptors are able to modulate morphine antinociception and tolerance during inflammatory pain. Here we used a mouse model to test the modulation of morphine effects by the selective sigma-1 antagonist S1RA (MR309), by determining its effect on inflammatory tactile allodynia (von Frey filaments) and on grip strength deficits induced by joint inflammation (a measure of pain-induced functional disability), and compared the results with those for nociceptive heat pain recorded with the unilateral hot plate (55 C) test. The subcutaneous (s.c.) administration of morphine induced antinociceptive effects to heat stimuli, and restored mechanical threshold and grip strength in mice with periarticular inflammation induced by Complete Freund’s Adjuvant. S1RA (80 mg/kg, s.c.) administered alone did not induce any effect on nociceptive heat pain or inflammatory allodynia, but was able to partially reverse grip strength deficits. The association of S1RA with morphine, at doses inducing little or no analgesic-like effects when administered alone, resulted in a marked antinociceptive effect to heat stimuli and complete reversion of inflammatory tactile allodynia. However, S1RA administration did not increase the effect of morphine on grip strength deficits induced by joint inflammation.MT was supported by a postdoctoral grant from the University of Granada.MR-C and IB-C were supported by FPU grants from the Spanish Ministry of Economy and Competitiveness (MINECO). This study was partially supported by the Spanish Ministry of Economy and Competitiveness (Grants SAF2013-47481P and SAF2016-80540-R), the Junta de Andalucía (Grant CTS109), and FEDER funds

Grip strength in mice with joint inflammation: A rheumatology function test sensitive to pain and analgesia

Grip strength deficit is a measure of pain-induced functional disability in rheumatic disease. We tested whether this parameter and tactile allodynia, the standard pain measure in preclinical studies, show parallels in their response to analgesics and basic mechanisms. Mice with periarticular injections of complete Freund's adjuvant (CFA) in the ankles showed periarticular immune infiltration and synovial membrane alterations, together with pronounced grip strength deficits and tactile allodynia measured with von Frey hairs. However, inflammation-induced tactile allodynia lasted longer than grip strength alterations, and therefore did not drive the functional deficits. Oral administration of the opioid drugs oxycodone (1–8 mg/kg) and tramadol (10–80 mg/kg) induced a better recovery of grip strength than acetaminophen (40–320 mg/kg) or the nonsteroidal antiinflammatory drugs ibuprofen (10–80 mg/kg) or celecoxib (40–160 mg/kg); these results are consistent with their analgesic efficacy in humans. Functional impairment was generally a more sensitive indicator of drug-induced analgesia than tactile allodynia, as drug doses that attenuated grip strength deficits showed little or no effect on von Frey thresholds. Finally, ruthenium red (a nonselective TRP antagonist) or the in vivo ablation of TRPV1-expressing neurons with resiniferatoxin abolished tactile allodynia without altering grip strength deficits, indicating that the neurobiology of tactile allodynia and grip strength deficits differ. In conclusion, grip strength deficits are due to a distinct type of pain that reflects an important aspect of the human pain experience, and therefore merits further exploration in preclinical studies to improve the translation of new analgesics from bench to bedside.This study was partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO, grant SAF2013-47481P), the Junta de Andalucía (grant CTS 109), and funding from Esteve and the European Regional Development Fund (FEDER)

TARGETING IMMUNE-DRIVEN OPIOID ANALGESIA BY SIGMA-1 RECEPTORS: OPENING THE DOOR TO NOVEL PERSPECTIVES FOR THE ANALGESIC USE OF SIGMA-1 ANTAGONISTS

Immune cells have a known role in pronociception, since they release a myriad of inflammatory algogens which interact with neurons to facilitate pain signaling. However, these cells also produce endogenous opioid peptides with analgesic potential. The sigma-1 receptor is a ligand-operated chaperone that modulates neurotransmission by interacting with multiple protein partners, including the µ-opioid receptor. We recently found that sigma-1 antagonists are able to induce opioid analgesia by enhancing the action of endogenous opioid peptides of immune origin during inflammation. This opioid analgesia is seen only at the inflamed site, where immune cells naturally accumulate. In this article we review the difficulties of targeting the opioid system for selective pain relief, and discuss the dual role of immune cells in pain and analgesia. Our discussion creates perspectives for possible novel therapeutic uses of sigma-1 antagonists as agents able to maximize the analgesic potential of the immune systemUniversity of GranadaMartín Escudero postdoctoral programFPU grants from the Spanish Ministry of Economy and Competitiveness (MINECO)Juan de la Cierva-Incorporación postdoctoral grant from MINECOMINECO [grant number SAF2016-80540-R]Junta de Andalucía (grant CTS109)FEDER fund

Sigma-1 receptors control neuropathic pain and macrophage infiltration into the dorsal root ganglion after peripheral nerve injury

Neuron-immune interaction in the dorsal root ganglia (DRG) plays a pivotal role in the neuropathic pain development after nerve injury. Sigma-1 receptor (Sig-1R) is expressed by DRG neurons but its role in neuropathic pain is not fully understood. We investigated the effect of peripheral Sig-1R on neuroinflammation in the DRG after spared (sciatic) nerve injury (SNI) in mice. Nerve injury induced a decrease in NeuN staining along with the nuclear eccentricity and ATF3 expression in the injured DRG. Sig-1R was present in all DRG neurons examined, and after SNI this receptor translocated to the periphery of the soma and the vicinity of the nucleus, especially in injured ATF3 + neurons. In WT mice, injured DRG produced the chemokine CCL2, and this was followed by massive infiltration of macrophages/monocytes, which clustered mainly around sensory neurons with translocated Sig-1R, accompanied by robust IL-6 increase and mechanical allodynia. In contrast, Sig-1R knockout (Sig-1R-KO) mice showed reduced levels of CCL2, decreased macrophage/monocyte infiltration into DRG, and less IL-6 and neuropathic mechanical allodynia after SNI. Our findings point to an important role of peripheral Sig-1R in sensory neuron-macrophage/monocyte communication in the DRG after peripheral nerve injury; thus, these receptors may contribute to the neuropathic pain phenotypeNeurofarmacología del dolor de la Universidad de Granada (CTS-109)FPU grants from the Spanish Ministry of Education, Culture and Sports.Spanish Ministry of Economy and Competitiveness (MINECO, grant SAF2016-80540-R)the Junta de Andalucía (grant CTS 109)Esteve PharmaceuticalsEuropean Regional Development Fund (ERDF

The sigma-1 receptor curtails endogenous opioid analgesia during sensitization of TRPV1 nociceptors

Background and Purpose: Peripheral sensitization contributes to pathological pain. While prostaglandin E2 (PGE2) and nerve growth factor (NGF) sensitize peptidergic C-nociceptors (TRPV1+), glial cell line-derived neurotrophic factor (GDNF) sensitizes non-peptidergic C-neurons (IB4+). Sigma-1 receptor (σ1R) is a Ca2+-sensing chaperone known to modulate analgesia induced by opioid drugs. This receptor binds both to TRPV1 and the µ-opioid receptor (MOPr), although the functional repercussions of these physical interactions in peripheral sensitization are unknown. Experimental Approach: We tested the effect of sigma-1 antagonism on PGE2-, NGF- and GDNF-induced mechanical and heat hyperalgesia in mice. We used immunohistochemistry to determine the presence of endomorphin-2, an endogenous MOPr agonist, on dorsal root ganglion (DRG) neurons. Recombinant proteins were used to study the interactions between σ1R, MOPr and TRPV1. We used calcium imaging to study the effects of sigma-1 antagonism on PGE2-induced sensitization of TRPV1+ nociceptors. Key Results: σ1R antagonists reversed PGE2- and NGF-induced hyperalgesia, but not GDNF-induced hyperalgesia. Endomorphin-2 was detected on TRPV1+ but not on IB4+ neurons. Peripheral opioid receptor antagonism by naloxone methiodide or administration of an anti-endomorphin-2 antibody to a sensitized paw, reversed the antihyperalgesia induced by sigma-1 antagonists. Sigma-1 antagonism transfers σ1R from TRPV1 to MOPr, suggesting that σ1R participate in TRPV1-MOPr crosstalk. Moreover, σ1R antagonism reversed, in a naloxone-sensitive manner, PGE2-induced sensitization of DRG neurons to the calcium flux elicited by capsaicin, the prototypic TRPV1 agonist. Conclusion and Implications: σ1R antagonism harnesses endogenous opioids produced by TRPV1+ neurons to reduce hyperalgesia by increasing MOPr activity