An inhibitor of neuronal exocytosis (DD04107) displays long-lasting in vivo activity against chronic inflammatory and neuropathic pain.

Small peptides patterned after the N terminus of the synaptosomal protein of 25 kDa, a member of the protein complex implicated in Ca(2+)-dependent neuronal exocytosis, inhibit in vitro the release of neuromodulators involved in pain signaling, suggesting an in vivo analgesic activity. Here, we report that compound DD04107 (palmitoyl-EEMQRR-NH(2)), a 6-mer palmitoylated peptide that blocks the inflammatory recruitment of ion channels to the plasma membrane of nociceptors and the release of calcitonin gene-related peptide from primary sensory neurons, displays potent and long-lasting in vivo antihyperalgesia and antiallodynia in chronic models of inflammatory and neuropathic pain, such as the complete Freund's adjuvant, osteosarcoma, chemotherapy, and diabetic neuropathic models. Subcutaneous administration of the peptide produced a dose-dependent antihyperalgesic and antiallodynic activity that lasted ≥24 h. The compound showed a systemic distribution, characterized by a bicompartmental pharmacokinetic profile. Safety pharmacology studies indicated that the peptide is largely devoid of side effects and substantiated that the in vivo activity is not caused by locomotor impairment. Therefore, DD04107 is a potent and long-lasting antinociceptive compound that displays a safe pharmacological profile. These findings support the notion that neuronal exocytosis of receptors and neuronal algogens pivotally contribute to chronic inflammatory and neuropathic pain and imply a central role of peptidergic nociceptor sensitization to the pathogenesis of pain.

Design and synthesis of indole-based peptoids as potent noncompetitive antagonists of transient receptor potential vanilloid 1.

The vanilloid receptor subunit 1, or transient receptor potential vanilloid 1 (TRPV1), integrates physical and chemical stimuli in the peripheral nervous system, playing a key role in inflammatory pain. Identification of potent TRPV1 antagonists is thus an important goal of current neuropharmacology. Herein, we describe the solid-phase synthesis of a series of indole-based peptoids (N-alkylglycines) and the biological activity of the peptoids as novel TRPV1 antagonists. The potency and selectivity of the compounds were determined by electrophysiological recordings in Xenopus oocytes. The most potent and selective noncompetitive TRPV1 antagonist of the series, compound 7, represents an interesting pharmacophoric structure for analgesic lead optimization.

Design and characterization of a noncompetitive antagonist of the transient receptor potential vanilloid subunit 1 channel with in vivo analgesic and anti-inflammatory activity.

UNLABELLED: Vanilloid receptor subunit 1 (TRPV1) is an integrator of physical and chemical stimuli in the peripheral nervous system. This receptor plays a key role in the pathophysiology of inflammatory pain. Thus, the identification of receptor antagonists with analgesic and anti-inflammatory activity in vivo is an important goal of current neuropharmacology. Here, we report that [L-arginyl]-[N-[2,4-dichlorophenethyl]glycyl]-N-(2,4-dichlorophenethyl) glycinamide (H-Arg-15-15C) is a channel blocker that abrogates capsaicin and pH-evoked TRPV1 channel activity with submicromolar activity. Compound H-Arg-15-15C preferentially inhibits TRPV1, showing marginal block of other neuronal receptors. Compound H-Arg-15-15C acts as a noncompetitive capsaicin antagonist with modest voltage-dependent blockade activity. The compound inhibited capsaicin-evoked nerve activity in afferent fibers without affecting mechanically activated activity. Notably, administration of compound H-Arg-15-15C prevented the irritant activity of a local administration of capsaicin and formalin and reversed the thermal hyperalgesia evoked by injection of complete Freund's adjuvant. Furthermore, it attenuated carrageenan-induced paw inflammation. Compound H-Arg-15-15C specifically decreased inflammatory conditions without affecting normal nociception. Taken together, these findings demonstrate that compound H-Arg-15-15C is a channel blocker of TRPV1 with analgesic and anti-inflammatory activity in vivo at clinically useful doses and substantiate the tenet that TRPV1 plays an important role in the etiology of chronic inflammatory pain. PERSPECTIVE: This study reports the design of a potent TRPV1 noncompetitive antagonist that exhibits anti-inflammatory and analgesic activity in preclinical models of acute and chronic pain. This compound is a lead for analgesic drug development.

Neuroprotection against excitotoxicity by N-alkylglycines in rat hippocampal neurons.

Excessive activation of glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype is considered a relevant initial step underlying different neurodegenerative diseases. Recently, with the approval of memantine to treat Alzheimer dementia, NMDA receptors have regained clinical interest. Accordingly, the development and validation of NMDA receptor antagonists is being reconsidered. We recently identified a family of trialkylglycines that act as channel blockers of the NMDAreceptor. Their neuroprotective activity against excitotoxic insults remains elusive. To address this issue, we first characterized the contribution of glutamate receptor subtypes to hippocampal death in culture as a function of days in culture in vitro (DIV). Whereas at 7 DIV neither NMDA nor glutamate produced a significant neuronal death, at 14 and 21 DIV, NMDA produced the death of 40% of the neurons exposed to this receptor agonist that was fully protected by MK-801. Similar results were obtained for L-glutamate at 14 DIV. In contrast, when neurons at 21 DIV were used, glutamate killed 51.1 +/- 4.9% of the neuronal population. This neuronal death was only partially prevented by MK-801, and fully abrogated by a combination of MK-801 and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Glucose deprivation injured 37.1 +/- 9.2% of the neurons through a mechanism sensitive to MK-801. The family of recently identified N-alkylglycines tested protected neurons against NMDA and glucosedeprivation toxicity, but not against glutamate toxicity. Noteworthy, N-alkylglicines with a moderate protection against NMDA-induced toxicity strongly protected from beta-amyloid toxicity. Collectively, these findings imply both NMDA and non-NMDA receptors in excitotoxicity of hippocampal neurons, and suggest that blockade of NMDA receptors alone may not suffice to efficiently abrogate neurodegeneration.