CR4056, a powerful analgesic imidazoline-2 receptor ligand, inhibits the inflammation-induced PKCε phosphorylation and membrane translocation in sensory neurons

Background and Purpose: CR4056 is a first-in-class imidazoline-2 (I2) receptor ligand characterized by potent analgesic activity in different experimental animal models of pain. In a recent phase II clinical trial, CR4056 effectively reduced pain in patients with knee osteoarthritis. In the present study, we investigated the effects of CR4056 on PKCε translocation in vitro and on PKCε activation in vivo in dorsal root ganglia (DRG) neurons. Experimental Approach: Effects of CR4056 on bradykinin-induced PKCε translocation were studied in rat sensory neurons by immunocytochemistry. PKCε activation was investigated by immunohistochemistry analysis of DRG from complete Freund's adjuvant-treated animals developing local hyperalgesia. The analgesic activity of CR4056 was tested on the same animals. Key Results: CR4056 inhibited PKCε translocation with very rapid and long-lasting activity. CR4056 decreased hyperalgesia and phospho-PKCε immunoreactivity in the DRG neurons innervating the inflamed paw. The effect of CR4056 on PKCε translocation was blocked by pertussis toxin, implying that the intracellular pathways involved Gi proteins. The inhibition of PKCε translocation by CR4056 was independent of the α2-adrenoeceptor and, surprisingly, was also independent of idazoxan-sensitive I2 binding sites. The I2 agonist 2BFI had no effect alone but potentiated the activity of low concentrations of CR4056. Conclusions and Implications: Our results demonstrate that CR4056 shares the ability to inhibit PKCε translocation with other analgesics. Whether the inhibition of PKCε involves binding to specific subtype(s) of I2 receptors should be further investigated. If so, this would be a new mode of action of a highly specific I2 receptor ligand

Analgesic efficacy of CR4056, a novel imidazoline-2 receptor ligand, in rat models of inflammatory and neuropathic pain

Flora Ferrari1, Simonetta Fiorentino1, Laura Mennuni1, Paolo Garofalo1, Ornella Letari1, Stefano Mandelli2, Antonio Giordani3, Marco Lanza1, Gianfranco Caselli11Department of Pharmacology and Toxicology; 2Department of Medicinal Chemistry; 3R&D Chemistry Drug Development and OS, Rottapharm S.p.A., Monza (MB), ItalyAbstract: Two decades of investigations have failed to unequivocally clarify the functions and the molecular nature of imidazoline-2 receptors (I2R). However, there is robust pharmacological evidence for the functional modulation of monoamino oxidase (MAO) and other important enzyme activities by I2 site ligands. Some compounds of this class proved to be active experimental tools in preventing both experimental pain and opioid tolerance and dependence. Unfortunately, even though these compounds bind with high potency to central I2 sites, they fail to represent a valid clinical opportunity due to their pharmacokinetic, selectivity or side-effects profile. This paper presents the preclinical profile of a novel I2 ligand (2-phenyl-6-(1H-imidazol-1yl)quinazoline; [CR4056]) that selectively inhibits the activity of human recombinant MAO-A in a concentration-dependent manner. A sub-chronic four day oral treatment of CR4056 increased norepinephrine (NE) tissue levels both in the rat cerebral cortex (63.1% ± 4.2%; P<0.05) and lumbar spinal cord (51.3% ± 6.7%; P < 0.05). In the complete Freund's adjuvant (CFA) rat model of inflammatory pain, CR4056 was found to be orally active (ED50 = 5.8 mg/kg, by mouth [p.o.]). In the acute capsaicin model, CR4056 completely blocked mechanical hyperalgesia in the injured hind paw (ED50 = 4.1 mg/kg, p.o.; ED100 = 17.9 mg/kg, p.o.). This effect was dose-dependently antagonized by the non-selective imidazoline I2/α2 antagonist idazoxan. In rat models of neuropathic pain, oral administration of CR4056 significantly attenuated mechanical hyperalgesia and allodynia. In summary, the present study suggests a novel pharmacological opportunity for inflammatory and/or neuropathic pain treatment based on selective interaction with central imidazoline-2 receptors.Keywords: imidazoline-2 receptors, hyperalgesia, allodynia, inflammatory pain, neuropathic pain, CR405

CR4056, a new analgesic I2 ligand, is highly effective against bortezomib-induced painful neuropathy in rats

Cristina Meregalli,1 Cecilia Ceresa,1 Annalisa Canta,1 Valentina Alda Carozzi,1 Alessia Chiorazzi,1 Barbara Sala,1 Norberto Oggioni,1 Marco Lanza,2 Ornella Letar,i2 Flora Ferrari,2 Federica Avezza,1 Paola Marmiroli,1 GianFranco Caselli,2 Guido Cavaletti11Department of Neuroscience and Biomedical Technologies, University of Milan-Bicocca, 2Pharmacology and Toxicology Department, Rottapharm | Madaus Research Center, Monza, ItalyAbstract: Although bortezomib (BTZ) is the frontline treatment for multiple myeloma, its clinical use is limited by the occurrence of painful peripheral neuropathy, whose treatment is still an unmet clinical need. Previous studies have shown chronic BTZ administration (0.20 mg/kg intravenously three times a week for 8 weeks) to female Wistar rats induced a peripheral neuropathy similar to that observed in humans. In this animal model of BTZ-induced neurotoxicity, the present authors evaluated the efficacy of CR4056, a novel I2 ligand endowed with a remarkable efficacy in several animal pain models. CR4056 was administered in a wide range of doses (0.6–60 mg/kg by gavage every day for 2–3 weeks) in comparison with buprenorphine (Bupre) (28.8 µg/kg subcutaneously every day for 2 weeks) and gabapentin (Gaba) (100 mg/kg by gavage every day for 3 weeks). Chronic administration of BTZ reduced nerve conduction velocity and induced allodynia. CR4056, Bupre, or Gaba did not affect the impaired nerve conduction velocity. Conversely, CR4056 dose-dependently reversed BTZ-induced allodynia (minimum effective dose 0.6 mg/kg). The optimal dose found, 6 mg/kg, provided a constant pain relief throughout the treatment period and without rebound after suspension, being effective when coadministered with BTZ, starting before or after allodynia was established, or when administered alone after BTZ cessation. A certain degree of tolerance was seen after 7 days of administration, but only at the highest doses (20 and 60 mg/kg). Bupre was effective only acutely, since tolerance was evident from the fourth day onwards. Gaba showed a significant activity only at the fourth day of treatment. CR4056, over the range of concentrations of 3–30 µM, was unable to hinder BTZ cytotoxicity on several tumor cell lines, which could indicate that this substance does not directly interfere with BTZ antitumor activity. Therefore, CR4056 could represent a new treatment option for BTZ-induced neuropathic pain.Keywords: imidazoline I2 receptor ligand, antinociception, allodynia, neuropathic pain, bortezomi

Induction of autophagic cell death by a novel molecule is increased by hypoxia

Adaptation to hypoxia through activation of the hypoxia inducible factor-1 (HIF-1) is crucial for tumor cells survival. Here we describe the antitumoral effects of the new molecule CR 3294 on tumor cells in the presence of hypoxia. Treatment of the breast carcinoma cell line MDA-MB-231 with CR 3294 in 1% O 2 resulted in an in vivo and in vitro inhibition of tumor growth. CR 3294 induced accumulation of autophagosomes in hypoxic MDA-MB-231 cells as assessed by both transmission electron microscopy (TEM) and the autophagic marker LC3-II. TEM analysis revealed the presence of invaginations of the cytoplasm into the nucleus. Autophagosomes were present in such invaginations. Moreover, CR 3294 inhibited both the DNA binding of HIF-1α and VEGF mRNA synthesis. Immunoprecipitation and immunofluorescence studies showed an interaction between LC3 and HIF-1α. We next detailed the effect of inhibitors and activators of autophagy on both HIF-1α and LC3. In particular, 3 methyladenine (3MA) and wortmannin, two macroautophagic inhibitors, prevented both the decrease of HIF-1α protein levels and LC3 processing in cells treated with CR 3294. Bafilomycin and leupeptin, inhibitors of lysosomes, prevented HIF-1α decrease without affecting LC3 processing. By contrast, treating hypoxic MDA-MB-231 cells with trifluoperazine (TFP) or serum withdrawal (SW), two activators of autophagy, diminished HIF-1α levels and stimulated LC3 processing. These results indicate that activation of the autophagic pathway in hypoxic cells by the new molecule CR 3294, as well as by TFP or SW, can have potentially important implications for cancer treatment. ©2008 Landes Bioscience

Synthesis and structure-activity relationship studies in serotonin 5-HT1A receptor agonists based on fused pyrrolidone scaffolds

A new class of serotonin 5-HT1A receptor ligands related to NAN-190, buspirone and aripiprazole has been designed using our potent 5-HT 3 receptor ligands as templates. The designed pyrrolidone derivatives 10a-n were prepared by means of the straightforward chemistry consisting in the reaction of the appropriate γ-haloester derivatives with the suitable arylpiperazinylalkylamines. The nanomolar 5-HT1A receptor affinity and the agonist-like profile shown by fused pyrrolidone derivatives 10k,m stimulated the rationalization of the interaction with an homology model of the 5-HT1A receptor and the evaluation of their selectivity profiles and the pharmacokinetic properties. Interestingly, the results of the profiling assays suggested for close congeners 10k,m a significantly divergent binding pattern with compound 10m showing an appreciable selectivity for 5-HT 1AR. © 2013 Elsevier Masson SAS. All rights reserved