ABSTRACT
The role of neuropeptide FF (NPFF) and its analogs in pain modulation is ambiguous. Although NPFF was first characterized as an antiopioid peptide, both antinociceptive and pronociceptive effects have been reported, depending on the route of administration. Currently, two NPFF receptors, termed FF1 and FF2, have been identified and cloned, but their roles in pain modulation remain elusive because of the lack of availability of selective compounds suitable for systemic administration in in vivo models. Ligand-binding studies confirm ubiquitous expression of both subtypes in brain, whereas only FF2 receptors are expressed spinally. This disparity in localization has served as the foundation of the hypothesis that FF1 receptors mediate the pronociceptive actions of NPFF. We have identified novel small molecule NPFF receptor agonists and antagonists with varying degrees of FF2/FF1 functional selectivity. Using these pharmacological tools in vivo has allowed us to define the roles of NPFF receptor subtypes as pertains to the modulation of nociception. We demonstrate that selective FF2 agonism does not modulate acute pain but instead ameliorates inflammatory and neuropathic pains. Treatment with a nonselective FF1/FF2 agonist potentiates allodynia in neuropathic rats and increases sensitivity to noxious thermal and to non-noxious mechanical stimuli in normal rats in an FF1 antagonist-reversible manner. Treatment with FF1 antagonists reversed established mechanical allodynia, indicating the possibility of increased NPFF tone through FF1 receptors. In conclusion, we provide evidence for the opposing roles of NPFF receptors and highlight selective FF2 agonism and/or selective FF1 antagonism as potential targets warranting further investigation.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Oligopeptides/metabolism , Receptors, Neuropeptide , Small Molecule Libraries/pharmacology , Animals , Anti-Inflammatory Agents, Non-Steroidal/administration & dosage , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Anti-Inflammatory Agents, Non-Steroidal/therapeutic use , Cyclic AMP/antagonists & inhibitors , Disease Models, Animal , Hyperalgesia/drug therapy , Hyperalgesia/metabolism , Ligands , Male , Mice , Mononeuropathies/drug therapy , Mononeuropathies/metabolism , NIH 3T3 Cells , Pain Measurement , Pain Threshold/drug effects , Rats , Receptors, Neuropeptide/agonists , Receptors, Neuropeptide/antagonists & inhibitors , Receptors, Neuropeptide/genetics , Small Molecule Libraries/administration & dosage , Small Molecule Libraries/chemistry , Small Molecule Libraries/therapeutic use , TransfectionABSTRACT
We report the discovery and initial characterization of a novel class of selective NPFF2 agonists. HTS screening using R-SAT, a whole cell based functional assay, identified a class of aryliminoguanidines as NPFF1 and NPFF2 ligands. Subsequent optimization led to molecules exhibiting selective NPFF2 agonistic activity. Systemic administration showed that selective NPFF2 agonists (1 and 3) are active in various pain models in vivo, whereas administration of a nonselective NPFF1 and NPFF2 agonist (9) increases sensitivity to noxious and non-noxious stimuli.
Subject(s)
Analgesics/chemical synthesis , Guanidines/chemical synthesis , Receptors, Neuropeptide/agonists , Analgesics/chemistry , Analgesics/pharmacology , Animals , Carrageenan , Guanidines/chemistry , Guanidines/pharmacology , Humans , In Vitro Techniques , Inflammation/chemically induced , Inflammation/drug therapy , Inflammation/physiopathology , Microsomes, Liver/metabolism , Pain/chemically induced , Pain/drug therapy , Pain/physiopathology , Pain Measurement , Peripheral Nervous System Diseases/drug therapy , Peripheral Nervous System Diseases/physiopathology , Rats , Receptors, Neuropeptide/antagonists & inhibitorsABSTRACT
Synthesis of (1R,3R,4S,7R)-7-hydroxy-1-hydroxymethyl-3-(2-N-isobutyroylguanin-9-yl)-2,5-dioxabicyclo[2.2.1]heptane (12), a protected alpha-L-LNA guanine nucleoside, has been accomplished using a convergent synthetic strategy starting from 1,2-di-O-acetylfuranose 4.
Subject(s)
Guanine , Oligonucleotides, Antisense/chemical synthesis , Indicators and Reagents , Molecular Structure , Nucleic Acid Conformation , Oligonucleotides , Oligonucleotides, Antisense/chemistryABSTRACT
The syntheses of monomeric nucleosides and 3'-O-phosphoramidite building blocks en route to alpha-L-ribo-configured locked nucleic acids (alpha-L-LNA), composed entirely of alpha-L-LNA monomers (alpha-L-ribo configuration) or of a mixture of alpha-L-LNA and DNA monomers (beta-D-ribo configuration), are described and the alpha-L-LNA oligomers are studied. Bicyclic 5-methylcytosin-1-yl and adenine-9-yl nucleoside derivatives have been prepared and the phosphoramidite approach has been used for the automated oligomerization leading to alpha-L-LNA oligomers. Binding studies revealed very efficient recognition of single-stranded DNA and RNA target oligonucleotide strands. Thus, stereoirregular alpha-L-LNA 11-mers containing a mixture of alpha-L-LNA monomers and DNA monomers ("mix-mer alpha-L-LNA") were shown to display DeltaT(m) values of +1 to +3 degrees C per modification toward DNA and +4 to +5 degrees C toward RNA when compared with the corresponding unmodified DNA x DNA and DNA x RNA reference duplexes. The corresponding DeltaT(m) values per modification for the stereoregular fully modified alpha-L-LNA were determined to be +4 degrees C (against DNA) and +5 degrees C (against RNA). 11-Mer alpha-L-LNAs (mix-mer alpha- L-LNA or fully modified alpha- L-LNA) were shown in vitro to be significantly stabilized toward 3'-exonucleolytic degradation. A duplex formed between RNA and either mix-mer alpha-L-LNA or fully modified alpha-L-LNA induced in vitro Escherichia coli RNase H-mediated cleavage, albeit very slow, of the RNA targets at high enzyme concentrations.
