Allosteric interactions between receptor site 3 and 4 of voltage-gated sodium channels: a novel perspective for the underlying mechanism of scorpion sting-induced pain

Antimicrobial, toxicological, and antigenic characteristics of three scorpion venoms from Colombia: Centruroides margaritatus, Tityus pachyurus and Tityus n. sp. aff. metuendus

The venom fractions of three buthid scorpion species from Colombia, C. margaritatus, T. pachyurus and T. n. sp. aff. metuendus, were examined for antimicrobial and toxicity toward mice and insects. The three venoms were separated into individual fractions using RP-HPLC, resulting in 85 fractions from C. margaritatus, 106 from T. pachyurus, and 70 from T. n. sp. aff. metuendus. The major fractions from the three scorpion venoms, which were eluted between 35 and 50 min, were tested for antimicrobial activity and toxicity. It was confirmed that the venom of the three species contains fractions with antimicrobial peptides that were evaluated against two bacterial strains of public health importance, Pseudomonas aeruginosa and Staphylococcus aureus. The venom of C. margaritatus had two antimicrobial fractions that showed activity against the named tested strains. The venom of T. pachyurus had three fractions that showed activity against S. aureus and two against both bacterial strains. Finally, the venom of T. n. sp. aff. metuendus had one fraction that showed activity against S. aureus, and five fractions showed activity against both bacterial strains. Also, some peptide fractions from the three venoms were toxic to mice. Last, the venoms of C. margaritatus and T. pachyurus were used as immunogens to obtain neutralizing antibodies against its respective venoms and to observe antibody recognition to related and unrelated scorpion venoms. A total of 15 mg of lyophilized antibodies were able to neutralize 1.5⋅LD50 of the venoms from T. n. sp. aff. metuendus, T. pachyurus and C. margaritatus, respectively. This information provides valuable insights into the diversity of each species' venom and their potential role in antimicrobial and venom toxicity.

Neuronomodulation of Excitable Neurons

Neuronomodulation refers to the modulation of neural conduction and synaptic transmission (i.e., the conduction process involved in synaptic transmission) of excitable neurons via changes in the membrane potential in response to chemical substances, from spillover neurotransmitters to paracrine or endocrine hormones circulating in the blood. Neuronomodulation can be direct or indirect, depending on the transduction pathways from the ligand binding site to the ion pore, either on the same molecule, i.e. the ion channel, or through an intermediate step on different molecules. The major players in direct neuronomodulation are ligand-gated or voltage-gated ion channels. The key process of direct neuronomodulation is the binding and chemoactivation of ligand-gated or voltage-gated ion channels, either orthosterically or allosterically, by various ligands. Indirect neuronomodulation involves metabotropic receptor-mediated slow potentials, where steroid hormones, cytokines, and chemokines can implement these actions. Elucidating neuronomodulation is of great significance for understanding the physiological mechanisms of brain function, and the occurrence and treatment of diseases.

Scorpion venom peptides: Molecular diversity, structural characteristics, and therapeutic use from channelopathies to viral infections and cancers

Animal venom is an important evolutionary innovation in nature. As one of the most representative animal venoms, scorpion venom contains an extremely diverse set of bioactive peptides. Scorpion venom peptides not only are 'poisons' that immobilize, paralyze, kill, or dissolve preys but also become important candidates for drug development and design. Here, the review focuses on the molecular diversity of scorpion venom peptides, their typical structural characteristics, and their multiple therapeutic or pharmaceutical applications in channelopathies, viral infections and cancers. Especially, the group of scorpion toxin TRPTx targeting transient receptor potential (TRP) channels is systematically summarized and worthy of attention because TRP channels play a crucial role in the regulation of homeostasis and the occurrence of diseases in human. We also further establish the potential relationship between the molecular characteristics and functional applications of scorpion venom peptides to provide a research basis for modern drug development and clinical utilization of scorpion venom resources.

Pain-related toxins in scorpion and spider venoms: a face to face with ion channels

Pain is a common symptom induced during envenomation by spiders and scorpions. Toxins isolated from their venom have become essential tools for studying the functioning and physiopathological role of ion channels, as they modulate their activity. In particular, toxins that induce pain relief effects can serve as a molecular basis for the development of future analgesics in humans. This review provides a summary of the different scorpion and spider toxins that directly interact with pain-related ion channels, with inhibitory or stimulatory effects. Some of these toxins were shown to affect pain modalities in different animal models providing information on the role played by these channels in the pain process. The close interaction of certain gating-modifier toxins with membrane phospholipids close to ion channels is examined along with molecular approaches to improve selectivity, affinity or bioavailability in vivo for therapeutic purposes.

Immortalized Dorsal Root Ganglion Neuron Cell Lines

Pain is one of the most significant causes of suffering and disability world-wide, and arguably the most burdensome global health challenge. The growing number of patients suffering from chronic pain conditions such as fibromyalgia, complex regional pain syndrome, migraine and irritable bowel syndrome, not only reflect the complexity and heterogeneity of pain types, but also our lack of understanding of the underlying mechanisms. Sensory neurons within the dorsal root ganglia (DRG) have emerged as viable targets for effective chronic pain therapy. However, DRG's contain different classes of primary sensory neurons including pain-associated nociceptive neurons, non-nociceptive temperature sensing, mechanosensory and chemoreceptive neurons, as well as multiple types of immune and endothelial cells. This cell-population heterogeneity makes investigations of individual subgroups of DRG neurons, such as nociceptors, difficult. In attempts to overcome some of these difficulties, a limited number of immortalized DRG-derived cell lines have been generated over the past few decades. In vitro experiments using DRG-derived cell lines have been useful in understanding sensory neuron function. In addition to retaining phenotypic similarities to primary cultured DRG neurons, these cells offer greater suitability for high throughput assays due to ease of culture, maintenance, growth efficiency and cost-effectiveness. For accurate interpretation and translation of results it is critical, however, that phenotypic similarities and differences of DRG-derived cells lines are methodically compared to native neurons. Published reports to date show notable variability in how these DRG-derived cells are maintained and differentiated. Understanding the cellular and molecular differences stemming from different culture methods, is essential to validate past and future experiments, and enable these cells to be used to their full potential. This review describes currently available DRG-derived cell lines, their known sensory and nociceptor specific molecular profiles, and summarize their morphological features related to differentiation and neurite outgrowth.

Toxins That Affect Voltage-Gated Sodium Channels

Voltage-gated sodium channels (VGSCs) are critical in generation and conduction of electrical signals in multiple excitable tissues. Natural toxins, produced by animal, plant, and microorganisms, target VGSCs through diverse strategies developed over millions of years of evolutions. Studying of the diverse interaction between VGSC and VGSC-targeting toxins has been contributing to the increasing understanding of molecular structure and function, pharmacology, and drug development potential of VGSCs. This chapter aims to summarize some of the current views on the VGSC-toxin interaction based on the established receptor sites of VGSC for natural toxins.