Synthesis and evaluation of aminobenzothiazoles as blockers of N- and T-type calcium channels

Inhibition of N-type calcium channels by phenoxyaniline and sulfonamide analogues

Building on previous investigations, structural modifications to the neuronal calcium ion channel blocker MONIRO-1 and related compounds were conducted that included replacement of the amide linker with an aniline and isosteric sulfonamide moiety, and the previously used strategy of substitution of the guanidinium group with less hydrophilic amine functionalities. A comprehensive SAR study revealed a number of phenoxyaniline and sulfonamide compounds that were more potent or had similar potency for the CaV2.2 and CaV3.2 channel compared to MONIRO-1 when evaluated in a FLIPR-based intracellular calcium response assay. Cytotoxicity investigations indicated that the sulfonamide analogues were well tolerated by Cos-7 cells at dosages required to inhibit both calcium ion channels. The sulfonamide derivatives were the most promising CaV2.2 inhibitors developed by us to date due, possessing high stability in plasma, low toxicity (estimated therapeutic index > 10), favourable CNS MPO scores (4.0-4.4) and high potency and selectivity, thereby, making this class of compounds suitable candidates for future in vivo studies.

Current Drug Development Overview: Targeting Voltage-Gated Calcium Channels for the Treatment of Pain

Voltage-gated calcium channels (VGCCs) are targeted to treat pain conditions. Since the discovery of their relation to pain processing control, they are investigated to find new strategies for better pain control. This review provides an overview of naturally based and synthetic VGCC blockers, highlighting new evidence on the development of drugs focusing on the VGCC subtypes as well as mixed targets with pre-clinical and clinical analgesic effects.

Role of ion channels in the mechanism of proteinuria (Review)

Proteinuria is a common clinical manifestation of kidney diseases, such as glomerulonephritis, nephrotic syndrome, immunoglobulin A nephropathy and diabetic nephropathy. Therefore, proteinuria is considered to be a risk factor for renal dysfunction. Furthermore, proteinuria is also significantly associated with the progression of kidney diseases and increased mortality. Its occurrence is closely associated with damage to the structure of the glomerular filtration membrane. An impaired glomerular filtration membrane can affect the selective filtration function of the kidneys; therefore, several macromolecular substances, such as proteins, may pass through the filtration membrane and promote the manifestation of proteinuria. It has been reported that ion channels play a significant role in the mechanisms underlying proteinuria. Ion channel mutations or other dysfunctions have been implicated in several diseases, therefore ion channels could be used as major therapeutic targets. The mechanisms underlying the action of ion channels and ion transporters in proteinuria have been overlooked in the literature, despite their importance in identifying novel targets for treating proteinuria and delaying the progression of kidney diseases. The current review article focused on the four key ion channel groups, namely Na⁺, Ca²⁺, Cl^- and K⁺ ion channels and the associated ion transporters.

Inhibition of N-type calcium ion channels by tricyclic antidepressants - experimental and theoretical justification for their use for neuropathic pain

A number of tricyclic antidepressants (TCAs) are commonly prescribed off-label for the treatment of neuropathic pain. The blockade of neuronal calcium ion channels is often invoked to partially explain the analgesic activity of TCAs, but there has been very limited experimental or theoretical evidence reported to support this assertion. The N-type calcium ion channel (CaV2.2) is a well-established target for the treatment of neuropathic pain and in this study a series of eleven TCAs and two closely related drugs were shown to be moderately effective inhibitors of this channel when endogenously expressed in the SH-SY5Y neuroblastoma cell line. A homology model of the channel, which matches closely a recently reported Cryo-EM structure, was used to investigate via docking and molecular dynamics experiments the possible mode of inhibition of CaV2.2 channels by TCAs. Two closely related binding modes, that occur in the channel cavity that exists between the selectivity filter and the internal gate, were identified. The TCAs are predicted to position themselves such that their ammonium side chains interfere with the selectivity filter, with some, such as amitriptyline, also appearing to hinder the channel's ability to open. This study provides the most comprehensive evidence to date that supports the notion that the blockade of neuronal calcium ion channels by TCAs is at least partially responsible for their analgesic effect.

Voltage-dependent CaV3.2 and CaV2.2 channels in nociceptive pathways

Noxious stimuli like cold, heat, pH change, tissue damage, and inflammation depolarize a membrane of peripheral endings of specialized nociceptive neurons which eventually results in the generation of an action potential. The electrical signal is carried along a long axon of nociceptive neurons from peripheral organs to soma located in dorsal root ganglions and further to the dorsal horn of the spinal cord where it is transmitted through a chemical synapse and is carried through the spinal thalamic tract into the brain. Two subtypes of voltage-activated calcium play a major role in signal transmission: a low voltage-activated Ca_V3.2 channel and a high voltage-activated Ca_V2.2 channel. The Ca_V3.2 channel contributes mainly to the signal conductance along nociceptive neurons while the principal role of the Ca_V2.2 channel is in the synaptic transmission at the dorsal horn. Both channels contribute to the signal initiation at peripheral nerve endings. This review summarizes current knowledge about the expression and distribution of these channels in a nociceptive pathway, the regulation of their expression and gating during pain pathology, and their suitability as targets for pharmacological therapy.

Synthesis and cytotoxic effects of 2-thio-3,4-dihydroquinazoline derivatives as novel T-type calcium channel blockers

In our previous work, a series of 2-amino-3,4-dihydroquinazoline derivativesusing an electron acceptor group was reported to be potent T-type calcium channel blockers and exhibit strong cytotoxic effects against various cancerous cell lines. To investigate the role of the guanidine moiety in the 2-amino-3,4-dihydroquinazoline scaffold as a pharmacophore for dual biological activity, a new series of 2-thio-3,4-dihydroquniazoline derivatives using an electron donor group at the C2-position was synthesized and evaluated for T-type calcium channel blocking activity and cytotoxic effects against two human cancerous cell lines (lung cancer A549 and colon cancer HCT-116). Among them, compound 6g showed potent inhibition of Ca_v3.2 currents (83% inhibition) at 10 µM concentrations. The compound also exhibited IC₅₀ values of 5.0 and 6.4 µM against A549 and HCT-116 cell lines, respectively, which are comparable to the parental lead compound KYS05090. These results indicate that the isothiourea moiety similar to the guanidine moiety of 2-amino-3,4-dihydroquinazoline derivatives may be an essential pharmacophore for the desired biological activities. Therefore, our preliminary work can provide the opportunity to expand a chemical repertoire to improve affinity and selectivity for T-type calcium channels.

High-Voltage-Activated Calcium Channel in the Afferent Pain Pathway: An Important Target of Pain Therapies

High-voltage-activated (HVA) Ca2+ channels are widely expressed in the nervous system. They play an important role in pain conduction by participating in various physiological processes such as synaptic transmission, changes in synaptic plasticity, and neuronal excitability. Available evidence suggests that the HVA channel is an important therapeutic target for pain management. In this review, we summarize the changes in different subtypes of HVA channel during pain and present the currently available evidence from the clinical application of HVA channel blockers. We also review novel drugs in various phases of development. Moreover, we discuss the future prospects of HVA channel blockers in order to promote "bench-to-bedside" translation.

Venomic, Transcriptomic, and Bioactivity Analyses of Pamphobeteus verdolaga Venom Reveal Complex Disulfide-Rich Peptides That Modulate Calcium Channels

Pamphobeteus verdolaga is a recently described Theraphosidae spider from the Andean region of Colombia. Previous reports partially characterized its venom profile. In this study, we conducted a detailed analysis that includes reversed-phase high-performance liquid chromatography (rp-HPLC), calcium influx assays, tandem mass spectrometry analysis (tMS/MS), and venom-gland transcriptome. rp-HPLC fractions of P. verdolaga venom showed activity on Ca_V2.2, Ca_V3.2, and Na_V1.7 ion channels. Active fractions contained several peptides with molecular masses ranging from 3399.4 to 3839.6 Da. The tMS/MS analysis of active fraction displaying the strongest activity to inhibit calcium channels showed sequence fragments similar to one of the translated transcripts detected in the venom-gland transcriptome. The putative peptide of this translated transcript corresponded to a toxin, here named ω-theraphositoxin-Pv3a, a potential ion channel modulator toxin that is, in addition, very similar to other theraphositoxins affecting calcium channels (i.e., ω-theraphotoxin-Asp1a). Additionally, using this holistic approach, we found that P. verdolaga venom is an important source of disulfide-rich proteins expressing at least eight superfamilies.