Merging Structural Motifs of Functionalized Amino Acids and α-Aminoamides Results in Novel Anticonvulsant Compounds with Significant Effects on Slow and Fast Inactivation of Voltage-Gated Sodium Channels and in the Treatment of Neuropathic Pain

Abstract

We recently reported that merging key structural pharmacophores of the anticonvulsant drugs lacosamide (a functionalized amino acid) with safinamide (an α-aminoamide) resulted in novel compounds with anticonvulsant activities superior to that of either drug alone. Here, we examined the effects of six such chimeric compounds on Na+-channel function in central nervous system catecholaminergic (CAD) cells. Using whole-cell patch clamp electrophysiology, we demonstrated that these compounds affected Na+ channel fast and slow inactivation processes. Detailed electrophysiological characterization of two of these chimeric compounds that contained either an oxymethylene ((R)-7) or a chemical bond ((R)-11) between the two aromatic rings showed comparable effects on slow inactivation, use-dependence of block, development of slow inactivation, and recovery of Na+ channels from inactivation. Both compounds were equally effective at inducing slow inactivation; (R)-7 shifted the fast inactivation curve in the hyperpolarizing direction greater than (R)-11, suggesting that in the presence of (R)-7, a larger fraction of the channels are in an inactivated state. None of the chimeric compounds affected veratridine- or KCl-induced glutamate release in neonatal cortical neurons. There was modest inhibition of KCl-induced calcium influx in cortical neurons. Finally, a single intraperitoneal administration of (R)-7, but not (R)-11, completely reversed mechanical hypersensitivity in a tibial-nerve injury model of neuropathic pain. The strong effects of (R)-7 on slow and fast inactivation of Na+ channels may contribute to its efficacy and provide a promising novel therapy for neuropathic pain, in addition to its antiepileptic potential.

Identification of the Benzyloxyphenyl Pharmacophore: A Structural Unit That Promotes Sodium Channel Slow Inactivation

“…Macroscopic sodium currents were blocked by (R)-5 almost as effectively as (R)-1 and (R)-2, 22,23 and (R)-6 was more potent than (R)-5 ( Figure 6A, B). Compared to control cells, peak macroscopic sodium currents were inhibited by ∼72% by (R)-5 (200 μM) and ∼74% by (R)-6 (30 μM) ( Figure 6B).…”

“…Importantly, our earlier SAR studies 10 demonstrated that considerable structural latitude exists for the 4′-aryl-extended unit in compounds such as 3, 4, and 6, and that these compounds exhibited excellent Na + channel slow and, in some cases, fast inactivation properties. 22 Currently, we are exploring the utility of this general pharmacophore unit for the design of novel neurological agents.…”

CRMP2 Protein SUMOylation Modulates NaV1.7 Channel Trafficking

“…Culturing CAD Cells and Transfection-The neuronally derived CAD cells were grown at 37°C and in 5% CO 2 as described previously (9,32,33). CAD cells were transfected with 1 g/l of polyethyleneimine (Sigma) (34) and 2 g of CRMP2, CRMP2-K374A, SUMO1-3, Ubc9, or SENP1/2 cDNAs plus EGFP plasmid (0.2 g).…”

Inhibition of Transmitter Release and Attenuation of Anti-retroviral-associated and Tibial Nerve Injury-related Painful Peripheral Neuropathy by Novel Synthetic Ca2+ Channel Peptides

“…Tibial Nerve Injury (TNI) Model of Peripheral NeuropathyThis procedure was completed as described previously (32). Under isoflurane (2%) anesthesia, the skin on the lateral surface of the thigh was incised, and a section was made directly through the biceps femoris muscle, exposing the sciatic nerve and its three terminal branches: the sural, common peroneal, and tibial nerves.…”