Targeting TRP channels for pain relief Brederson, Jill-Desiree; Kym, Philip R.; Szallasi, Arpad
European journal of pharmacology,
09/2013, Letnik:
716, Številka:
1-3
Journal Article
Recenzirano
Preclinical research has recently uncovered new molecular mechanisms underlying the generation and transduction of pain, many of which represent opportunities for pharmacological intervention. ...Manipulating temperature-sensitive Transient Receptor Potential (TRP) channels (so-called “thermoTRPs”) on nociceptive neurons is a particularly attractive strategy in that it targets the beginning of the pain pathway. In the focus of current drug development efforts are the heat-sensitive TRPV1, warm-activated TRPV3, cold-responsive TRPA1, and cool-activated TRPM8 channels. TRPV1 desensitization by topical agonists (e.g. high concentration capsaicin creams and patches) has been in clinical use for decades to alleviate chronic painful conditions like diabetic neuropathy. Currently, site-specific resiniferatoxin (an ultrapotent capsaicin analogue) injections are being evaluated as “molecular scalpels” to achieve permanent analgesia in cancer patients with chronic, intractable pain. In the past few years a number of potent, small molecule TRPV1, TRPV3 and TRPA1 antagonists have been advanced into clinical trials for the treatment of inflammatory, neuropathic and visceral pain. TRPM8 antagonists are following closely behind for cold allodynia. Early TRPV1 antagonists in the clinic, however, showed worrisome adverse effects including hyperthermia and impaired noxious heat sensation. These adverse effects placed the patients at risk for scalding injury and prompted their withdrawal from the clinical trials. Second generation TRPV1 antagonists that do not cause core body temperature elevation have been reported, although the therapeutic utility of this class of compounds is not yet known. This review discusses the promise and challenges of developing TRP channel antagonists as a new generation of pain therapeutics.
Background:
There is growing evidence supporting a role for TRPA1 receptors in the neurotransmission of peripheral mechanical stimulation. In order to enhance understanding of TRPA1 contributions to ...mechanotransmission, we examined the effects a selective TRPA1 receptor antagonist, A-967079, on spinal neuronal activity following peripheral mechanical stimulation in uninjured, CFA-inflamed, and osteoarthritc (OA) rats.
Results:
Systemic injection of A-967079 (30 μmol/kg, i.v.) decreased the responses of wide dynamic range (WDR), and nociceptive specific (NS) neurons following noxious pinch stimulation of the ipsilateral hind paw in uninjured and CFA-inflamed rats. Similarly, A-967079 reduced the responses of WDR neurons to high-intensity mechanical stimulation (300 g von Frey hair) of the knee joint in both OA and OA-sham rats. WDR neuronal responses to low-intensity mechanical stimulation (10 g von Frey hair) were also reduced by A-967079 administration to CFA-inflamed rats, but no effect was observed in uninjured rats. Additionally, the spontaneous activity of WDR neurons was decreased after A-967079 injection in CFA-inflamed rats but was unaltered in uninjured, OA, and OA-sham animals.
Conclusions:
Blockade of TRPA1 receptors disrupts transmission of high-intensity mechanical stimulation to the spinal cord in both uninjured and injured rats indicating that TRPA1 receptors have an important role in noxious mechanosensation in both normal and pathological conditions. TRPA1 receptors also contribute to the transmission of low-intensity mechanical stimulation, and to the modulation of spontaneous WDR firing, but only after an inflammatory injury.
Despite the increasing interest in TRPA1 channel as a pain target, its role in cold sensation and body temperature regulation is not clear; the efficacy and particularly side effects resulting from ...channel blockade remain poorly understood. Here we use a potent, selective, and bioavailable antagonist to address these issues. A-967079 potently blocks human (IC
50: 51
nmol/L, electrophysiology, 67
nmol/L, Ca
2+ assay) and rat TRPA1 (IC
50: 101
nmol/L, electrophysiology, 289
nmol/L, Ca
2+ assay). It is >1000-fold selective over other TRP channels, and is >150-fold selective over 75 other ion channels, enzymes, and G-protein-coupled receptors. Oral dosing of A-967079 produces robust drug exposure in rodents, and exhibits analgesic efficacy in allyl isothiocyanate-induced nocifensive response and osteoarthritic pain in rats (ED
50: 23.2
mg/kg, p.o.). A-967079 attenuates cold allodynia produced by nerve injury but does not alter noxious cold sensation in naive animals, suggesting distinct roles of TRPA1 in physiological and pathological states. Unlike TRPV1 antagonists, A-967079 does not alter body temperature. It also does not produce locomotor or cardiovascular side effects. Collectively, these data provide novel insights into TRPA1 function and suggest that the selective TRPA1 blockade may present a viable strategy for alleviating pain without untoward side effects.
Selective blockade of TRPA1 channel attenuates pathological pain without altering noxious cold sensation or body temperature regulation.
Objective
The aim was to demonstrate that continuous s.c. infusion of a soluble levodopa (LD)/carbidopa (CD) phosphate prodrug combination effectively delivers stable LD exposure via a minimally ...invasive and convenient mode and has the potential to treat Parkinson's disease (PD) patients who are not well controlled on oral medication.
Methods
Foslevodopa and foscarbidopa were prepared and the equilibrium solubility and chemical stability examined in aqueous media with different values of pH. Solutions of foslevodopa/foscarbidopa (ratios ranging from 4:1 to 20:1) were prepared by dissolving pH‐adjusted lyophilized materials in water and infused s.c. in healthy volunteers for ≤72 hours. Frequent blood samples were collected to measure LD and CD exposure, and safety was monitored throughout the study.
Results
Foslevodopa/foscarbidopa (ABBV‐951) demonstrates high water solubility and excellent chemical stability near physiological pH, enabling continuous s.c. infusion therapy. After s.c. infusion, a stable LD pharmacokinetic (PK) profile was maintained for ≤72 hours, and the infusion was well tolerated.
Interpretation
Preparation of foslevodopa and foscarbidopa enables preclinical and clinical PK, safety, and tolerability studies in support of their advancement for the treatment of PD. In phase 1 clinical trials, foslevodopa/foscarbidopa demonstrates consistent and stable LD plasma exposure, supporting further studies of this treatment as a potentially transformational option for those suffering from PD. ANN NEUROL 2021;90:52–61
An overview of Parkinson’s disease (PD) prevalence, diagnosis, and currently available treatment options is provided. A comprehensive list of different classes of marketed pharmaceutical drug ...products and the syntheses of various drug substances are summarized based on published literature.
The paramount importance of synthetic organic chemistry in the pharmaceutical industry arises from the necessity to physically prepare all designed molecules to obtain key data to feed the ...design–synthesis–data cycle, with the medicinal chemist at the center of this cycle. Synthesis specialists accelerate the cycle of medicinal chemistry innovation by rapidly identifying and executing impactful synthetic methods and strategies to accomplish project goals, addressing the synthetic accessibility bottleneck that often plagues discovery efforts. At AbbVie, Discovery Synthesis Groups (DSGs) such as Centralized Organic Synthesis (COS) have been deployed as embedded members of medicinal chemistry teams, filling the gap between discovery and process chemistry. COS chemists provide synthetic tools, scaffolds, and lead compounds to fuel the pipeline. Examples of project contributions from neuroscience, cystic fibrosis, and virology illustrate the impact of the DSG approach. In the first ten years of innovative science in pursuit of excellence in synthesis, several advanced drug candidates, including ABBV-2222 (galicaftor) for cystic fibrosis and foslevodopa/foscarbidopa for Parkinson’s disease, have emerged with key contributions from COS.
Elongation factor P (EF-P) accelerates diprolyl synthesis and requires a posttranslational modification to maintain proteostasis. Two phylogenetically distinct EF-P modification pathways have been ...described and are encoded in the majority of Gram-negative bacteria, but neither is present in Gram-positive bacteria. Prior work suggested that the EF-P-encoding gene (efp) primarily supports Bacillus subtilis swarming differentiation, whereas EF-P in Gram-negative bacteria has a more global housekeeping role, prompting our investigation to determine whether EF-P is modified and how it impacts gene expression in motile cells. We identified a 5-aminopentanol moiety attached to Lys32 of B. subtilis EF-P that is required for swarming motility. A fluorescent in vivo B. subtilis reporter system identified peptide motifs whose efficient synthesis was most dependent on 5-aminopentanol EF-P. Examination of the B. subtilis genome sequence showed that these EF-P-dependent peptide motifs were represented in flagellar genes. Taken together, these data show that, in B. subtilis, a previously uncharacterized posttranslational modification of EF-P can modulate the synthesis of specific diprolyl motifs present in proteins required for swarming motility.
Early assessment of crystalline thermodynamic solubility continues to be elusive for drug discovery and development despite its critical importance, especially for the ever-increasing fraction of ...poorly soluble drug candidates. Here we present a detailed evaluation of a physics-based free energy perturbation (FEP+) approach for computing the thermodynamic aqueous solubility. The predictive power of this approach is assessed across diverse chemical spaces, spanning pharmaceutically relevant literature compounds and more complex AbbVie compounds. Our approach achieves predictive (RMSE = 0.86) and differentiating power (R 2 = 0.69) and therefore provides notably improved correlations to experimental solubility compared to state-of-the-art machine learning approaches that utilize quantum mechanics-based descriptors. The importance of explicit considerations of crystalline packing in predicting solubility by the FEP+ approach is also highlighted in this study. Finally, we show how computed energetics, including hydration and sublimation free energies, can provide further insights into molecule design to feed the medicinal chemistry DMTA cycle.
Abundantly expressed in pain-sensing neurons, TRPV1, TRPA1 and TRPM8 are major cellular sensors of thermal, chemical and mechanical stimuli. The function of these ion channels has been attributed to ...their selective permeation of small cations (e.g., Ca2+, Na+ and K+), and the ion selectivity has been assumed to be an invariant fingerprint to a given channel. However, for TRPV1, the notion of invariant ion selectivity has been revised recently. When activated, TRPV1 undergoes time and agonist-dependent pore dilation, allowing permeation of large organic cations such as Yo-Pro and NMDG+. The pore dilation is of physiological importance, and has been exploited to specifically silence TRPV1-positive sensory neurons. It is unknown whether TRPA1 and TRPM8 undergo pore dilation. Here we show that TRPA1 activation by reactive or non-reactive agonists induces Yo-Pro uptake, which can be blocked by TRPA1 antagonists. In outside-out patch recordings using NMDG+ as the sole external cation and Na+ as the internal cation, TRPA1 activation results in dynamic changes in permeability to NMDG+. In contrast, TRPM8 activation does not produce either Yo-Pro uptake or significant change in ion selectivity. Hence, pore dilation occurs in TRPA1, but not in TRPM8 channels.
Elongation factor P (EF-P) is a ubiquitous bacterial protein that is required for the synthesis of poly-proline motifs during translation. In Escherichia coli and Salmonella enterica, the ...posttranslational β-lysylation of Lys34 by the PoxA protein is critical for EF-P activity. PoxA is absent from many bacterial species such as Pseudomonas aeruginosa, prompting a search for alternative EF-P posttranslation modification pathways. Structural analyses of P. aeruginosa EF-P revealed the attachment of a single cyclic rhamnose moiety to an Arg residue at a position equivalent to that at which β-Lys is attached to E. coli EF-P. Analysis of the genomes of organisms that both lack poxA and encode an Arg32-containing EF-P revealed a highly conserved glycosyltransferase (EarP) encoded at a position adjacent to efp. EF-P proteins isolated from P. aeruginosa ΔearP, or from a ΔrmlC::acc1 strain deficient in dTDP-L-rhamnose biosynthesis, were unmodified. In vitro assays confirmed the ability of EarP to use dTDP-L-rhamnose as a substrate for the posttranslational glycosylation of EF-P. The role of rhamnosylated EF-P in translational control was investigated in P. aeruginosa using a Pro4-green fluorescent protein (Pro4GFP) in vivo reporter assay, and the fluorescence was significantly reduced in Δefp, ΔearP, and ΔrmlC::acc1 strains. ΔrmlC::acc1, ΔearP, and Δefp strains also displayed significant increases in their sensitivities to a range of antibiotics, including ertapenem, polymyxin B, cefotaxim, and piperacillin. Taken together, our findings indicate that posttranslational rhamnosylation of EF-P plays a key role in P. aeruginosa gene expression and survival.
Infections with pathogenic Salmonella, E. coli, and Pseudomonas isolates can all lead to infectious disease with potentially fatal sequelae. EF-P proteins contribute to the pathogenicity of the causative agents of these and other diseases by controlling the translation of proteins critical for modulating antibiotic resistance, motility, and other traits that play key roles in establishing virulence. In Salmonella spp. and E. coli, the attachment of β-Lys is required for EF-P activity, but the proteins required for this posttranslational modification pathway are absent from many organisms. Instead, bacteria such as P. aeruginosa activate EF-P by posttranslational modification with rhamnose, revealing a new role for protein glycosylation that may also prove useful as a target for the development of novel antibiotics.