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Human α-calcitonin gene-related peptide (h-α-CGRP) is a highly potent vasodilator peptide that belongs to the family of calcitonin peptides. There are two forms of CGRP receptors in humans and rodents: α-CGRP receptor predominately found in the cardiovascular system and β-CGRP receptor predominating in the gastrointestinal tract. The CGRP receptors are primarily localized to C and Aδ sensory fibers, where they are involved in nociceptive transmission and migraine pathophysiology. These fibers are found both peripherally and centrally, with extensive perivascular location. The CGRP receptors belong to the class B G-protein-coupled receptors, and they are primarily associated to signaling via Gα proteins. The objectives of the present work were: (i) synthesis of three single-labelled fluorescent analogues of h-α-CGRP by 9-fluorenylmethyloxycarbonyl (Fmoc)-based solid-phase peptide synthesis, and (ii) testing of their biological activity in isolated human, mouse, and rat arteries by using a small-vessel myograph setup. The three analogues were labelled with 5(6)-carboxyfluorescein via the spacer 6-aminohexanoic acid at the chain of Lys or Lys. Circular dichroism (CD) experiments were performed to obtain information on the secondary structure of these fluorescently labelled peptides. The CD spectra indicated that the folding of all three analogues was similar to that of native α-CGRP. The three fluorescent analogues of α-CGRP were successfully prepared with a purity of >95%. In comparison to α-CGRP, the three analogues exhibited similar efficacy, but different potency in producing a vasodilator effect. The analogue labelled at the N-terminus proved to be the most readily synthesized, but it was found to possess the lowest vasodilator potency. The analogues labelled at Lys or Lys exhibited an acceptable reduction in potency (i.e., 3-5 times and 5-10 times less potent, respectively), and thus they have potential for use in further investigations of receptor internalization and neuronal reuptake.
Learn More >AIMS The covalent linking of non-steroidal anti-inflammatory drugs (NSAIDs) to a hydrogen sulfide (H2S)-releasing moiety has been shown to dramatically reduce gastrointestinal (GI) damage and bleeding, as well as increasing anti-inflammatory and analgesic potency. We have tested the hypothesis that a H2S-releasing derivative of ketoprofen (ATB-352) would exhibit enhanced efficacy without significant GI damage in a mouse model of allodynia/hyperalgesia. RESULTS ATB-352 was significantly more potent as an analgesic than ketoprofen, and did not elicit GI damage. Pretreatment with a cannabinoid receptor-1 antagonist (AM251) significantly reduced the analgesic effects of ATB-352. The CB-1 antagonist exacerbated GI damage when co-administered with ketoprofen, but GI damage was not induced by the combination of ATB-352 and the CB-1 antagonist. ATB-352 was substantially more potent than ketoprofen as an inhibitor of fatty acid amide hydrolase, consistent with a contribution of endogenous cannabinoids to the analgesic effects of this drug. Blood anandamide levels were significantly depressed by ketoprofen, but remained unchanged after treatment with ATB-352. INNOVATION Ketoprofen is a potent analgesic, but its clinical use is significantly limited by its propensity to cause significant ulceration and bleeding in the GI tract. Covalently linking an H2S-releasing moiety to ketoprofen profoundly reduces the GI toxicity of the drug, while boosting the analgesic effectiveness.
Learn More >γ-Aminobutyric acid (GABA) uptake transporters are membrane transport proteins that are involved in the pathophysiology of a number of neurological disorders. Some types of chronic pain appear to result from the dysfunction of the GABAergic system. The deficiency of mouse GAT1 transporter (mGAT1) abolishes the nociceptive response, which means that mGAT1 inhibition is an appropriate medical approach to achieve analgesia. The mGAT4 transporter is the second most abundant GAT subtype in the brain; however, its physiological role has not yet been fully understood in the central nervous system. In this study, we examined whether the combination of mGAT1 and mGAT3/mGAT4 inhibition in a single molecule might lead to potentially synergistic effects improving analgesic activity to relieve neuropathic pain. To study this hypothesis, new GABA uptake inhibitors were designed, synthesized, and evaluated in terms of their activity and subtype selectivity for mGAT1-4. Among new functionalized amino acid derivatives of serine and GABA analogs, compounds with preferential mGAT3/4 inhibitory activity were discovered. Two selected hits (19b and 31c) were subjected to in vivo tests. We found a statistically significant antiallodynic activity in the von Frey test in diabetic and oxaliplatin-induced neuropathic pain model. The novel compounds (4-hydroxybutanoic, 4-hydroxypentanoic, and 4-aminobutanoic acid derivatives and serine analogs) provide new insights into the structure-activity relationship of mGAT3/mGAT4 inhibitors and indicate a new direction in the search for potential treatment of neuropathic pain of various origin.
Learn More >Endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenous lipids that activate cannabinoid receptors. Activation of these receptors produces anti-inflammatory and analgesic effects. Fatty acid amide hydrolase (FAAH) is a membrane enzyme that hydrolases endocannabinoids, thus inhibition of FAAH represents an attractive approach to develop new therapeutics for treating inflammation and pain. Previously, potent rat FAAH inhibitors containing 2-naphthyl- and 4-phenylthiazole scaffolds were identified, but up to the present time, very little structure-activity relationship (SAR) studies have been performed on these moieties. We designed and synthesized several analogs containing these structural motifs and evaluated their inhibition potencies against human FAAH enzyme. In addition, we built and validated a homology model of human FAAH enzyme and performed docking experiments. We identified several inhibitors in the low nanomolar range and calculated their ADME predicted values. These FAAH inhibitors represent promising drug candidates for future preclinical in vivo studies.
Learn More >We designed and synthesized a novel series of piperidine propionamide derivatives as potent sigma-1 (σ) receptor antagonists and mu (μ) opioid receptor agonists, and measured their affinity for σ and μ receptors in vitro through binding assays. The basic scaffold of the new compounds contained a 4-substituted piperidine ring and N-aryl propionamide. Compound 44, N-(2-(4-(4-fluorobenzyl) piperidin-1-yl) ethyl)-N-(4-methoxy-phenyl) propionamide, showed the highest affinity for σ receptor (K σ = 1.86 nM) and μ receptor (K μ = 2.1 nM). It exhibited potent analgesic activity in the formalin test (ED = 15.1 ± 1.67 mg/kg) and had equivalent analgesic effects to S1RA (σ antagonist) in a CCI model. Therefore, Compound 44, which has mixed σ/μ receptor profiles, may be a potential candidate for treating neuropathic pain.
Learn More >Large (big)-conductance calcium-activated potassium (BK) channels are expressed in migraine-related structures such as the cranial arteries, trigeminal ganglion and trigeminal spinal nucleus, and they play a substantial role in vascular tonus and neuronal excitability. Using synthetic BK channels openers was associated with headache as a frequent adverse effect in healthy volunteers. Additionally, BK channels are downstream molecules in migraine signalling pathways that are activated by several compounds known to provoke migraine, including calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP) and glyceryl trinitrate (GTN). Also, there is a high affinity and a close coupling between BK channels and ATP-sensitive potassium (K) channels, the role of which has recently been established in migraine pathophysiology. These observations raise the question as to whether direct BK channel activation can provoke migraine in migraine patients, and whether the BK channel could be a potential novel anti-migraine target. Hence, randomized and placebo-controlled clinical studies on BK channel openers or blockers in migraine patients are needed.
Learn More >The pivotal role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology was identified over 30 years ago, but the successful clinical development of targeted therapies has only recently been realized. This perspective traces the decades long evolution of medicinal chemistry required to advance small molecule CGRP receptor antagonists, also called gepants, including the current clinical agents: rimegepant, vazegepant, ubrogepant and atogepant. Providing clinically effective blockade of CGRP signaling required surmounting multiple challenging hurdles, including defeating a sizeable ligand with subnanomolar affinity for its receptor, designing antagonists with an extended confirmation and multiple pharmacophores while retaining solubility and oral bioavailability, and achieving circulating free plasma levels that provided near maximal CGRP receptor coverage. The clinical efficacy of oral and intranasal gepants and the injectable CGRP monoclonal antibodies (mAbs) are described, as are recent synthetic developments which have benefited from new structural biology data. The first oral gepant was recently approved and heralds a new era in the treatment of migraine.
Learn More >Lipopolysaccharide (LPS) or repeated water avoidance stress (WAS) induces visceral allodynia and colonic hyperpermeability via corticotropin-releasing factor (CRF) and proinflammatory cytokines, which is considered to be a rat irritable bowel syndrome (IBS) model. As losartan is known to inhibit proinflammatory cytokine release, we hypothesized that it improves these visceral changes.
Learn More >Metastatic breast cancer is prevalent worldwide, and one of the most common sites of metastasis are long bones. Of patients with disease, the major symptom is pain, yet current medications fail to adequately result in analgesic efficacy and present major undesirable adverse effects. In our study we investigate the potential of a novel monoacylglycerol lipase (MAGL) inhibitor, MJN110, in a murine model of cancer induced bone pain (CIBP). Literature has previously demonstrated that MAGL inhibitors function to increase the endogenous concentrations of 2-arachydonylglycerol, which then activate CB1 and CB2 receptors inhibiting inflammation and pain. We demonstrate that administration of MJN110 significantly and dose-dependently alleviates spontaneous pain behavior during acute administration compared to vehicle control. In addition, the MJN110 maintains its efficacy in a chronic dosing paradigm over the course of 7 days without signs of receptor sensitization. In vitro analysis of MJN110 demonstrated a dose dependent and significant decrease in cell viability of 66.1 breast adenocarcinoma cells and to a greater extent than KML29, an alternate MAGL inhibitor, or the CB2 agonist JWH015. Chronic administration of the compound did not appear to affect tumor burden evidenced by radiograph or histological analysis. Together, these data support the application for MJN110 as a novel therapeutic for cancer induced bone pain. SIGNIFICANCE STATEMENT: Current standard of care for metastatic breast cancer pain is opioid-based therapies with adjunctive chemotherapy, which have highly addictive and other deleterious side effects. The need for effective, non-opioid based therapies is essential and harnessing the endogenous cannabinoid system is proving to be a new target to treat various types of pain conditions. We present a novel drug targeting the endogenous cannabinoid system that is effective at reducing pain in a mouse model of metastatic breast cancer to bone.
Learn More >: Atopic dermatitis (AD) is a type of allergic/inflammatory dermatitis characterized by itch and an impairment in quality of life.: Herein, the authors review drug discovery efforts for AD, highlighting the clinical efficacy of novel drugs, with a particular focus on the relief of pruritus. Topical agents include emollients, topical antihistamines, corticosteroids, calcineurin inhibitors and herbs. Recently, topical phosphodiesterase E4 (PDE4) inhibitors like crisaborole have become available and are efficacious for mild to moderate AD with few side effects. For more severe AD, monoclonal antibodies like dupilumab are considered as efficacious subcutaneous treatment options. In severe and recalcitrant AD, systemic treatment can ameliorate AD symptoms.: Many topical and systemic medications have demonstrated therapeutic benefits for AD. Indeed, randomized trials have shown that topical PDE4 inhibitors and subcutaneous dupilumab are safe and efficacious. Objective tools to evaluate itch and gauge treatment efficacy is important, but current methodology relies primarily on clinical scores. AD is a systemic atopic disease with a lot of complicated psychosocial issues. Suboptimal efficacy is often due to poor compliance and unrealistic expectation of curative treatment, rendering treatment difficult despite the existence of effective medications.
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