The dorsal root ganglion (DRG) is the primary neuron responsible for transmitting peripheral pain signals to the central nervous system and plays a crucial role in pain transduction. Modulation of DRG excitability is considered a viable approach for pain management. Neuronal excitability is intricately linked to the ion channels on the neurons. The small and medium-sized DRG neurons are chiefly engaged in pain conduction and have high levels of TTX-S sodium channels, with Nav1.7 accounting for approximately 80% of the current. Voltage-gated sodium channel (VGSC or Nav) blockers are vital targets for the management of central nervous system diseases, particularly chronic pain. VGSCs play a key role in controlling cellular excitability. Clinical research has shown that Nav1.7 plays a crucial role in pain sensation, and there is strong genetic evidence linking Nav1.7 and its encoding gene SCN9A gene to painful disorders in humans. Many studies have shown that Nav1.7 plays an important role in pain management. The role of Nav1.7 in pain signaling pathways makes it an attractive target for the potential development of new pain drugs. Meanwhile, understanding the architecture of Nav1.7 may help to develop the next generation of painkillers. This review provides updates on the recently reported molecular inhibitors targeting the Nav1.7 pathway, summarizes their structure-activity relationships (SARs), and discusses their therapeutic effects on painful diseases. Pharmaceutical chemists are working to improve the therapeutic index of Nav1.7 inhibitors, achieve better analgesic effects, and reduce side effects. We hope that this review will contribute to the development of novel Nav1.7 inhibitors as potential drugs.

This study reports that targeting intrinsically disordered regions of the voltage-gated sodium channel 1.7 (NaV1.7) protein facilitates discovery of sodium channel inhibitory peptide aptamers (NaViPA) for adeno-associated virus-mediated (AAV-mediated), sensory neuron-specific analgesia. A multipronged inhibition of INa1.7, INa1.6, INa1.3, and INa1.1 - but not INa1.5 and INa1.8 - was found for a prototype and named NaViPA1, which was derived from the NaV1.7 intracellular loop 1, and is conserved among the TTXs NaV subtypes. NaViPA1 expression in primary sensory neurons (PSNs) of dorsal root ganglia (DRG) produced significant inhibition of TTXs INa but not TTXr INa. DRG injection of AAV6-encoded NaViPA1 significantly attenuated evoked and spontaneous pain behaviors in both male and female rats with neuropathic pain induced by tibial nerve injury (TNI). Whole-cell current clamp of the PSNs showed that NaViPA1 expression normalized PSN excitability in TNI rats, suggesting that NaViPA1 attenuated pain by reversal of injury-induced neuronal hypersensitivity. IHC revealed efficient NaViPA1 expression restricted in PSNs and their central and peripheral terminals, indicating PSN-restricted AAV biodistribution. Inhibition of sodium channels by NaViPA1 was replicated in the human iPSC-derived sensory neurons. These results summate that NaViPA1 is a promising analgesic lead that, combined with AAV-mediated PSN-specific block of multiple TTXs NaVs, has potential as a peripheral nerve-restricted analgesic therapeutic.

BACKGROUND: Zanthoxylum bungeanum Maxim. (Z. bungeanum), a member of the Rutaceae family, has a rich history of traditional use in Asia for treating arthritis and toothache conditions. As characteristic chemical components, numerous kinds of alkaloids have been extracted from plants and their diverse biological activities have been reported. However, research on the isoquinoline alkaloid, a specific type of alkaloids, in Z. bungeanum was scarce.
OBJECTIVE: The study aimed to isolate a novel isoquinoline alkaloid from Z. bungeanum and explore its pharmacological activity in vitro and analgesic activity in vivo.
METHODS: Isoquinoline alkaloid isolation and identification from Z. bungeanum were conducted using chromatographic and spectroscopic methods. The whole-cell patch-clamp technique was applied to assess its impact on neuronal excitability, and endogenous voltage-gated potassium (Kv) and sodium (Nav) currents in acutely isolated mouse small-diameter dorsal root ganglion (DRG) neurons. Its inhibitory impacts on channels were further validated with HEK293 cells stably expressing Nav1.7 and Nav1.8, and Chinese hamster ovary (CHO) cells transiently expressing Kv2.1. The formalin inflammatory pain model was utilized to evaluate the potential analgesic activity in vivo.
RESULTS: A novel isoquinoline alkaloid named HJ-69 (N-13-(3-methoxyprop-1-yl)rutaecarpine) was isolated and identified from Z. bungeanum for the first time. HJ-69 significantly suppressed the firing frequency and amplitudes of action potentials in DRG neurons. Consistently, it state-dependently inhibited endogenous Nav currents of DRG neurons, with half maximal inhibitory concentration (IC50) values of 13.06 ± 2.06 μM and 30.19 ± 2.07 μM for the inactivated and resting states, respectively. HJ-69 significantly suppressed potassium currents in DRG neurons, which notably inhibited the delayed rectifier potassium (IK) currents (IC50 = 6.95 ± 1.29 μM) and slightly affected the transient outward potassium (IA) currents (IC50 = 523.50 ± 39.16 μM). Furtherly, HJ-69 exhibited similar potencies on heterologously expressed Nav1.7, Nav1.8, and Kv2.1 channels, which correspondingly represent the main components in neurons. Notably, intraperitoneal administration of 30 mg/kg and 100 mg/kg HJ-69 significantly alleviated pain behaviors in the mouse inflammatory pain model induced by formalin.
CONCLUSIONS: The study concluded that HJ-69 is a novel and active isoquinoline alkaloid, and the inhibition of Nav and Kv channels contributes to its analgesic activity. HJ-69 may be a promising prototype for future analgesic drug discovery based on the isoquinoline alkaloid.

The NaV1.8 channel, mainly found in the peripheral nervous system, is recognized as one of the key factors in chronic pain. The molecule VX-150 was initially promising in targeting this channel, but the phase II trials of VX-150 did not show expected pain relief results. By analyzing the interaction mode of VX-150 and NaV1.8, we developed two series with a total of 19 molecules and examined their binding affinity to NaV1.8 in vitro and analgesic effect in vivo. One compound, named 2j, stood out with notable activity against the NaV1.8 channel and showed effective pain relief in models of chronic inflammatory pain and neuropathic pain. Our research points to 2j as a strong contender for developing safer pain-relief treatments.

Ion channels, transporters, and other ion-flux controlling proteins, collectively comprising the \"ion permeome\", are common drug targets, however, their roles in cancer remain understudied. Our integrative pan-cancer transcriptome analysis shows that genes encoding the ion permeome are significantly more often highly expressed in specific subsets of cancer samples, compared to pan-transcriptome expectations. To enable target selection, we identified 410 survival-associated IP genes in 33 cancer types using a machine-learning approach. Notably, GJB2 and SCN9A show prominent expression in neoplastic cells and are associated with poor prognosis in glioblastoma, the most common and aggressive brain cancer. GJB2 or SCN9A knockdown in patient-derived glioblastoma cells induces transcriptome-wide changes involving neuron projection and proliferation pathways, impairs cell viability and tumor sphere formation in vitro, perturbs tunneling nanotube dynamics, and extends the survival of glioblastoma-bearing mice. Thus, aberrant activation of genes encoding ion transport proteins appears as a pan-cancer feature defining tumor heterogeneity, which can be exploited for mechanistic insights and therapy development.

UNASSIGNED: Pain is a significant global health issue, and the current treatment options for pain management have limitations in terms of effectiveness, side effects, and potential for addiction. There is a pressing need for improved pain treatments and the development of new drugs. Voltage-gated sodium channels, particularly Nav1.3, Nav1.7, Nav1.8, and Nav1.9, play a crucial role in neuronal excitability and are predominantly expressed in the peripheral nervous system. Targeting these channels may provide a means to treat pain while minimizing central and cardiac adverse effects. In this study, we construct protein-protein interaction (PPI) networks based on pain-related sodium channels and develop a corresponding drug-target interaction network to identify potential lead compounds for pain management. To ensure reliable machine learning predictions, we carefully select 111 inhibitor data sets from a pool of more than 1000 targets in the PPI network. We employ 3 distinct machine learning algorithms combined with advanced natural language processing (NLP)-based embeddings, specifically pretrained transformer and autoencoder representations. Through a systematic screening process, we evaluate the side effects and repurposing potential of more than 150,000 drug candidates targeting Nav1.7 and Nav1.8 sodium channels. In addition, we assess the ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties of these candidates to identify leads with near-optimal characteristics. Our strategy provides an innovative platform for the pharmacological development of pain treatments, offering the potential for improved efficacy and reduced side effects.

The Nav1.7 voltage-gated sodium channel plays a key role in nociception. Three functional variants in the SCN9A gene (encoding M932L, V991L, and D1908G in Nav1.7), have recently been identified as stemming from Neanderthal introgression and to associate with pain symptomatology in UK BioBank data. In 1000 genomes data, these variants are absent in Europeans but common in Latin Americans. Analysing high-density genotype data from 7594 Latin Americans, we characterized Neanderthal introgression in SCN9A. We find that tracts of introgression occur on a Native American genomic background, have an average length of ~123 kb and overlap the M932L, V991L, and D1908G coding positions. Furthermore, we measured experimentally six pain thresholds in 1623 healthy Colombians. We found that Neanderthal ancestry in SCN9A is significantly associated with a lower mechanical pain threshold after sensitization with mustard oil and evidence of additivity of effects across Nav1.7 variants. Our findings support the reported association of Neanderthal Nav1.7 variants with clinical pain, define a specific sensory modality affected by archaic introgression in SCN9A and are consistent with independent effects of the Neanderthal variants on Nav1.7 function.

Licorice is a traditional Chinese medicine and recorded to have pain relief effects in national pharmacopoeia, but the mechanisms behind these effects have not been fully explored. Among the hundreds of compounds in licorice, licochalcone A (LCA) and licochalcone B (LCB) are two important components belonging to the chalcone family. In this study, we compared the analgesic effects of these two licochalcones and the molecular mechanisms. LCA and LCB were applied in cultured dorsal root ganglion (DRG) neurons, and the voltage-gated sodium (NaV) currents and action potentials were recorded. The electrophysiological experiments showed that LCA can inhibit NaV currents and dampen excitabilities of DRG neurons, whereas LCB did not show inhibition effect on NaV currents. Because the NaV1.7 channel can modulate Subthreshold membrane potential oscillations in DRG neuron, which can palliate neuropathic pain, HEK293T cells were transfected with NaV1.7 channel and recorded with whole-cell patch clamp. LCA can also inhibit NaV1.7 channels exogenously expressed in HEK293T cells. We further explored the analgesic effects of LCA and LCB on formalin-induced pain animal models. The animal behavior tests revealed that LCA can inhibit the pain responses during phase 1 and phase 2 of formalin test, and LCB can inhibit the pain responses during phase 2. The differences of the effects on NaV currents between LCA and LCB provide us with the basis for developing NaV channel inhibitors, and the novel findings of analgesic effects indicate that licochalcones can be developed into effective analgesic medicines. SIGNIFICANCE STATEMENT: This study found that licochalcone A (LCA) can inhibit voltage-gated sodium (NaV) currents, dampen excitabilities of dorsal root ganglion neurons, and inhibit the NaV1.7 channels exogenously expressed in HEK293T cells. Animal behavior tests showed that LCA can inhibit the pain responses during phase 1 and phase 2 of formalin test, whereas licochalcone B can inhibit the pain responses during phase 2. These findings indicate that licochalcones could be the leading compounds for developing NaV channel inhibitors and effective analgesic medicines.

Voltage-gated sodium channel 1.7 (Nav1.7) remains one of the most promising drug targets for pain relief. In the current study, we conducted a high-throughput screening of natural products in our in-house compound library to discover novel Nav1.7 inhibitors, then characterized their pharmacological properties. We identified 25 naphthylisoquinoline alkaloids (NIQs) from Ancistrocladus tectorius to be a novel type of Nav1.7 channel inhibitors. Their stereostructures including the linkage modes of the naphthalene group at the isoquinoline core were revealed by a comprehensive analysis of HRESIMS, 1D, and 2D NMR spectra as well as ECD spectra and single-crystal X-ray diffraction analysis with Cu Kα radiation. All the NIQs showed inhibitory activities against the Nav1.7 channel stably expressed in HEK293 cells, and the naphthalene ring in the C-7 position displayed a more important role in the inhibitory activity than that in the C-5 site. Among the NIQs tested, compound 2 was the most potent with an IC50 of 0.73 ± 0.03 µM. We demonstrated that compound 2 (3 µM) caused dramatical shift of steady-state slow inactivation toward the hyperpolarizing direction (V1/2 values were changed from -39.54 ± 2.77 mV to -65.53 ± 4.39 mV, which might contribute to the inhibition of compound 2 against the Nav1.7 channel. In acutely isolated dorsal root ganglion (DRG) neurons, compound 2 (10 μM) dramatically suppressed native sodium currents and action potential firing. In the formalin-induced mouse inflammatory pain model, local intraplantar administration of compound 2 (2, 20, 200 nmol) dose-dependently attenuated the nociceptive behaviors. In summary, NIQs represent a new type of Nav1.7 channel inhibitors and may act as structural templates for the following analgesic drug development.

Chronic pain, as an unmet medical need, severely impacts the quality of life. The voltage-gated sodium channel NaV1.7 preferentially expressed in sensory neurons of dorsal root ganglia (DRG) serves a promising target for pain therapy. Here, we report the design, synthesis, and evaluation of a series of acyl sulfonamide derivatives targeting Nav1.7 for their antinociceptive activities. Among the derivatives tested, the compound 36c was identified as a selective and potent NaV1.7 inhibitor in vitro and exhibited antinociceptive effects in vivo. The identification of 36c not only provides a new insight into the discovery of selective NaV1.7 inhibitors, but also may hold premise for pain therapy.