A modulator of the low-voltage-activated T-type calcium channel that reverses HIV glycoprotein 120-, paclitaxel-, and spinal nerve ligation-induced peripheral neuropathies

Animal models of neuropathic pain

Animal models continue to be crucial to developing our understanding of the molecular, cellular, and neurophysiological mechanisms that lead to neuropathic pain. The overwhelming majority of animal studies use rodent models, ranging from surgical and trauma-induced models to those induced by metabolic diseases, genetic mutations, viruses, neurotoxic drugs, and cancer. We discuss the clinical relevance of the available models and the pain behavior tests commonly used as outcome measures. Finally, we summarize the refinements that have been proposed to improve the ability of animal model studies to predict clinical efficacy.

C-H Functionalization-Enabled 11-Step Semisynthesis of (-)-Veragranine A and Characterization of Synthetic Analogs in Osteoarthritis-related Pain Treatment

We report an efficient semisynthesis of the cholestane steroidal alkaloid (-)-veragranine A with a 6/6/6/5/6/6 hexacyclic ring system, eight stereocenters, and a unique C12-C23 linkage. Our synthesis features a Schönecker-Baran C-H oxidation at C12, a Suzuki-Miyaura cross-coupling to form the C12-C23 bond, and a hydrogen atom transfer (HAT)-initiated Minisci C-H cyclization to forge the C20-C22 bond with desired stereochemistry at C20. These enabling transformations significantly enhanced the overall synthetic efficiency and delivered (-)-veragranine A in 11 steps and over 200 mg from cheap and readily available dehydroepiandrosterone. In addition, this approach allowed flexible syntheses of novel synthetic analogs for biological evaluations in sensory neurons in vitro and in an in vivo model of arthritic pain, from which two novel lead compounds were identified for further development.

Nav1.7 Modulator Bearing a 3-Hydroxyindole Backbone Holds the Potential to Reverse Neuropathic Pain

Chronic pain is a growing global health problem affecting at least 10% of the world's population. However, current chronic pain treatments are inadequate. Voltage-gated sodium channels (Navs) play a pivotal role in regulating neuronal excitability and pain signal transmission and thus are main targets for nonopioid painkiller development, especially those preferentially expressed in dorsal root ganglial (DRG) neurons, such as Nav1.6, Nav1.7, and Nav1.8. In this study, we screened in virtual hits from dihydrobenzofuran and 3-hydroxyoxindole hybrid molecules against Navs via a veratridine (VTD)-based calcium imaging method. The results showed that one of the molecules, 3g, could inhibit VTD-induced neuronal activity significantly. Voltage clamp recordings demonstrated that 3g inhibited the total Na+ currents of DRG neurons in a concentration-dependent manner. Biophysical analysis revealed that 3g slowed the activation, meanwhile enhancing the inactivation of the Navs. Additionally, 3g use-dependently blocked Na+ currents. By combining with selective Nav inhibitors and a heterozygous expression system, we demonstrated that 3g preferentially inhibited the TTX-S Na+ currents, specifically the Nav1.7 current, other than the TTX-R Na+ currents. Molecular docking experiments implicated that 3g binds to a known allosteric site at the voltage-sensing domain IV(VSDIV) of Nav1.7. Finally, intrathecal injection of 3g significantly relieved mechanical pain behavior in the spared nerve injury (SNI) rat model, suggesting that 3g is a promising candidate for treating chronic pain.

An up-to-date view of paclitaxel-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN),referring to the damage to the peripheral nerves caused by exposure to a neurotoxic chemotherapeutic agent, is a common side effect amongst patients undergoing chemotherapy. Paclitaxel-induced peripheral neuropathy (PIPN) can lead to dose reduction or early cessation of chemotherapy, which is not conducive to patients'survival. Even after treatment is discontinued, PIPN symptoms carried a greater risk of worsening and plagued the patient's life, leading to long-term morbidity in survivors. Here, we summarize the research progress for clinical manifestations, risk factors, pathogenesis, prevention and treatment of PIPN, so as to embark on the path of preventing PIPN with prolongation of patient's life quality on a long-term basis.

Ion channels regulate energy homeostasis and the progression of metabolic disorders: Novel mechanisms and pharmacology of their modulators

The progression of metabolic diseases, featured by dysregulated metabolic signaling pathways, is orchestrated by numerous signaling networks. Among the regulators, ion channels transport ions across the membranes and trigger downstream signaling transduction. They critically regulate energy homeostasis and pathogenesis of metabolic diseases and are potential therapeutic targets for treating metabolic disorders. Ion channel blockers have been used to treat diabetes for decades by stimulating insulin secretion, yet with hypoglycemia and other adverse effects. It calls for deeper understanding of the largely elusive regulatory mechanisms, which facilitates the identification of new therapeutic targets and safe drugs against ion channels. In the article, we critically assess the two principal regulatory mechanisms, protein-channel interaction and post-translational modification on the activities of ion channels to modulate energy homeostasis and metabolic disorders through multiple novel mechanisms. Moreover, we discuss the multidisciplinary methods that provide the tools for elucidation of the regulatory mechanisms mediating metabolic disorders by ion channels. In terms of translational perspective, the mechanistic analysis of recently validated ion channels that regulate insulin resistance, body weight control, and adverse effects of current ion channel antagonists are discussed in details. Their small molecule modulators serve as promising new drug candidates to combat metabolic disorders.

Synthesis and In Vivo Antiarrhythmic Activity Evaluation of Novel Scutellarein Analogues as Voltage-Gated Nav1.5 and Cav1.2 Channels Blockers

Malignant cardiac arrhythmias with high morbidity and mortality have posed a significant threat to our human health. Scutellarein, a metabolite of Scutellarin which is isolated from Scutellaria altissima L., presents excellent therapeutic effects on cardiovascular diseases and could further be metabolized into methylated forms. A series of 22 new scutellarein derivatives with hydroxyl-substitution based on the scutellarin metabolite in vivo was designed, synthesized via the conjugation of the scutellarein scaffold with pharmacophores of FDA-approved antiarrhythmic medications and evaluated for their antiarrhythmic activity through the analyzation of the rat number of arrhythmia recovery, corresponding to the recovery time and maintenance time in the rat model of barium chloride-induced arrhythmia, as well as the cumulative dosage of aconitine required to induce VP, VT, VF and CA in the rat model of aconitine-induced arrhythmia. All designed compounds could shorten the time of the arrhythmia continuum induced by barium chloride, indicating that 4'-hydroxy substituents of scutellarein had rapid-onset antiarrhythmic effects. In addition, nearly all of the compounds could normalize the HR, RR, QRS, QT and QTc interval, as well as the P/T waves' amplitude. The most promising compound 10e showed the best antiarrhythmic activity with long-term efficacy and extremely low cytotoxicity, better than the positive control scutellarein. This result was also approved by the computational docking simulation. Most importantly, patch clamp measurements on Nav1.5 and Cav1.2 channels indicated that compound 10e was able to reduce the INa and ICa in a concentration-dependent manner and left-shifted the inactivation curve of Nav1.5. Taken together, all compounds were considered to be antiarrhythmic. Compound 10e even showed no proarrhythmic effect and could be classified as Ib Vaughan Williams antiarrhythmic agents. What is more, compound 10e did not block the hERG potassium channel which highly associated with cardiotoxicity.

T-type calcium channel modulation by hydrogen sulfide in neuropathic pain conditions

Neuropathic pain can appear as a direct or indirect nerve damage lesion or disease that affects the somatosensory nervous system. If the neurons are damaged or indirectly stimulated, immune cells contribute significantly to inflammatory and neuropathic pain. After nerve injury, peripheral macrophages/spinal microglia accumulate around damaged neurons, producing endogenous hydrogen sulfide (H₂S) through the cystathionine-γ-lyase (CSE) enzyme. H₂S has a pronociceptive modulation on the Ca_v3.2 subtype, the predominant Ca_v3 isoform involved in pain processes. The present review provides relevant information about H₂S modulation on the Ca_v3.2 T-type channels in neuropathic pain conditions. We have discussed that the dual effect of H₂S on T-type channels is concentration-dependent, that is, an inhibitory effect is seen at low concentrations of 10 µM and an augmentation effect on T-current at 100 µM. The modulation mechanism of the Ca_v3.2 channel by H₂S involves the direct participation of the redox/Zn²⁺ affinity site located in the His191 in the extracellular loop of domain I of the channel, involving a group of extracellular cysteines, comprising C114, C123, C128, and C1333, that can modify the local redox environment. The indirect interaction pathways involve the regulation of the Ca_v3.2 channel through cytokines, kinases, and post-translational regulators of channel expression. The findings conclude that the CSE/H₂S/Ca_v3.2 pathway could be a promising therapeutic target for neuropathic pain disorders.

Stereospecific Effects of Benzimidazolonepiperidine Compounds on T-Type Ca2+ Channels and Pain

T-type calcium channels activate in response to subthreshold membrane depolarizations and represent an important source of Ca²⁺ influx near the resting membrane potential. These channels regulate neuronal excitability and have been linked to pain. For this reason, T-type calcium channels are suitable molecular targets for the development of new non-opioid analgesics. Our previous work identified an analogue of benzimidazolonepiperidine, 5bk, that preferentially inhibited Ca_V3.2 channels and reversed mechanical allodynia. In this study, we synthesized and screened a small library of 47 compounds derived from 5bk. We found several compounds that inhibited the Ca²⁺ influx in DRG neurons of all sizes. After separating the enantiomers of each active compound, we found two compounds, 3-25-R and 3-14-3-S, that potently inhibited the Ca²⁺ influx. Whole-cell patch clamp recordings from small- to medium-sized DRG neurons revealed that both compounds decreased total Ca²⁺. Application of 3-14-3-S (but not 3-25-R) blocked transiently expressed Ca_V3.1-3.3 channels with a similar IC₅₀ value. 3-14-3-S decreased T-type, but not N-type, Ca²⁺ currents in DRG neurons. Furthermore, intrathecal delivery of 3-14-3-S relieved tonic, neuropathic, and inflammatory pain in preclinical models. 3-14-3-S did not exhibit any activity against G protein-coupled opioid receptors. Preliminary docking studies also suggest that 3-14-3-S can bind to the central pore domain of T-type channels. Together, our chemical characterization and functional and behavioral data identify a novel T-type calcium channel blocker with in vivo efficacy in experimental models of tonic, neuropathic, and inflammatory pain.

Modulation of Adaptive Immunity and Viral Infections by Ion Channels

Most cellular functions require of ion homeostasis and ion movement. Among others, ion channels play a crucial role in controlling the homeostasis of anions and cations concentration between the extracellular and intracellular compartments. Calcium (Ca2+) is one of the most relevant ions involved in regulating critical functions of immune cells, allowing the appropriate development of immune cell responses against pathogens and tumor cells. Due to the importance of Ca2+ in inducing the immune response, some viruses have evolved mechanisms to modulate intracellular Ca2+ concentrations and the mobilization of this cation through Ca2+ channels to increase their infectivity and to evade the immune system using different mechanisms. For instance, some viral infections require the influx of Ca2+ through ionic channels as a first step to enter the cell, as well as their replication and budding. Moreover, through the expression of viral proteins on the surface of infected cells, Ca2+ channels function can be altered, enhancing the pathogen evasion of the adaptive immune response. In this article, we review those ion channels and ion transporters that are essential for the function of immune cells. Specifically, cation channels and Ca2+ channels in the context of viral infections and their contribution to the modulation of adaptive immune responses.

Reversal of Bortezomib-Induced Neurotoxicity by Suvecaltamide, a Selective T-Type Ca-Channel Modulator, in Preclinical Models

Simple Summary

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a side-effect of anti-cancer medications, which can lead to pain, disruptions to movement, and eventually results in the need to interrupt or stop chemotherapy. This study sought to test whether the drug suvecaltamide could help to reduce the impact of the chemotherapy agent bortezomib (BTZ) on symptoms of CIPN using animal models and human cells. Suvecaltamide did reverse negative changes in nerve conduction velocity and intraepidermal nerve fiber density indicative of CIPN in rats, and did not interfere with the anti-cancer effect of BTZ. These results indicate that suvecaltamide could potentially be useful for patients experiencing CIPN, although further mechanistic and molecular studies in vitro and in vivo are required before clinical trials.

Abstract

This study evaluated suvecaltamide, a selective T-type calcium channel modulator, on chemotherapy-induced peripheral neurotoxicity (CIPN) and anti-cancer activity associated with bortezomib (BTZ). Rats received BTZ (0.2 mg/kg thrice weekly) for 4 weeks, then BTZ alone (n = 8) or BTZ+suvecaltamide (3, 10, or 30 mg/kg once daily; each n = 12) for 4 weeks. Nerve conduction velocity (NCV), mechanical threshold, β-tubulin polymerization, and intraepidermal nerve fiber (IENF) density were assessed. Proteasome inhibition was evaluated in peripheral blood mononuclear cells. Cytotoxicity was assessed in human multiple myeloma cell lines (MCLs) exposed to BTZ alone (IC₅₀ concentration), BTZ+suvecaltamide (10, 30, 100, 300, or 1000 nM), suvecaltamide alone, or vehicle. Tumor volume was estimated in athymic nude mice bearing MCL xenografts receiving vehicle, BTZ alone (1 mg/kg twice weekly), or BTZ+suvecaltamide (30 mg/kg once daily) for 28 days, or no treatment (each n = 8). After 4 weeks, suvecaltamide 10 or 30 mg/kg reversed BTZ-induced reduction in NCV, and suvecaltamide 30 mg/kg reversed BTZ-induced reduction in IENF density. Proteasome inhibition and cytotoxicity were similar between BTZ alone and BTZ+suvecaltamide. BTZ alone and BTZ+suvecaltamide reduced tumor volume versus the control (day 18), and BTZ+suvecaltamide reduced tumor volume versus BTZ alone (day 28). Suvecaltamide reversed CIPN without affecting BTZ anti-cancer activity in preclinical models.

Chemotherapy-Induced Peripheral Neuropathy: Mechanisms and Therapeutic Avenues

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious and often persistent adverse consequence of certain chemotherapeutic agents. It is a major dose-limiting factor of many first-line chemotherapies, affecting 20-50% of patients at standard doses and nearly all patients at high doses. As cancer survivorship continues to increase with improvements in early diagnosis and treatment, more patients will experience CIPN despite completing cancer treatment, which interferes with recovery, leading to chronic pain and worsening quality of life. The National Cancer Institute has identified CIPN as a priority in translational research. To date, there are no FDA-approved drugs for preventing or treating CIPN, with emerging debate on mechanisms and promising new targets. This review highlights current literature and suggests novel approaches to CIPN based on proposed mechanisms of action that aim either to confer neuroprotection against chemotherapy-induced neurotoxicity or reverse the downstream effects of painful neuropathy.

Targeting T-type/CaV3.2 channels for chronic pain

T-type calcium channels regulate neuronal excitability and are important contributors of pain processing. CaV3.2 channels are the major isoform expressed in nonpeptidergic and peptidergic nociceptive neurons and are emerging as promising targets for pain treatment. Numerous studies have shown that CaV3.2 expression and/or activity are significantly increased in spinal dorsal horn and in dorsal root ganglia neurons in different inflammatory and neuropathic pain models. Pharmacological campaigns to inhibit the functional expression of CaV3.2 for treatment of pain have focused on the development of direct channel blockers, but none have produced lead candidates. Targeting the proteins that regulate the trafficking or transcription, and the ones that modify the channels via post-translational modifications are alternative means to regulate expression and function of CaV3.2 channels and hence to develop new drugs to control pain. Here we synthesize data supporting a role for CaV3.2 in numerous pain modalities and then discuss emerging opportunities for the indirect targeting of CaV3.2 channels.