Gonyautoxins: First evidence in pain management in total knee arthroplasty

Gonyautoxins 2/3 Local Periarticular Injection for Pain Management after Total Knee Arthroplasty: A Double-Blind, Randomized Study

The purpose of this study was to compare the efficacy of periarticular infiltration of gonyautoxin 2/3 (GTX 2/3) and a mixture of levobupivacaine, ketorolac, and epinephrine for pain management after total knee arthroplasty (TKA). Forty-eight patients were randomly allocated to receive periarticular infiltration of 40 µg GTX 2/3 (n = 24) diluted in 30 mL of sodium chloride 0.9% (study group) or a combination of 300 mg of levobupivacaine, 1 mg of epinephrine, and 60 mg ketorolac (n = 24) diluted in 150 mL of sodium chloride 0.9% (control group). Intraoperative anesthetic and surgical techniques were identical for both groups. Postoperatively, all patients received patient-controlled analgesia (morphine bolus of 1 mg; lockout interval of 8 minutes), acetaminophen, and ketoprofen for 72 hours. A blinded investigator recorded morphine consumption, which was the primary outcome. Also, the range of motion (ROM) and static and dynamic pain were assessed at 6, 12, 36, and 60 hours after surgery. The incidence of adverse events, time to readiness for discharge, and length of hospital stay were also recorded. The median of total cumulative morphine consumption was 16 mg (range, 0-62 mg) in the GTX 2/3 group and 9 mg (range, 0-54 mg) in control group, which did not reach statistical difference (median test, p = 0.40). Furthermore, static and dynamic pain scores were similar at all time intervals. GTX 2/3 was inferior in range of motion at 6 and 12 hours; nevertheless, we noted no difference after 36 hours. No differences between groups were found in terms of complications, side effects, or length of hospital stay. No significant differences were found between groups in terms of breakthrough morphine requirement. However, local anesthetic use resulted in an increased ROM in the first 12 hours. This prospective randomized clinical trial shows that GTX 2/3 is a safe and efficient drug for pain control after TKA; nevertheless, more studies using GTX 2/3 with larger populations are needed to confirm the safety profile and efficiency. This is level 1 therapeutic study, randomized, double-blind clinical trial.

Marine Cyanobacteria as Sources of Lead Anticancer Compounds: A Review of Families of Metabolites with Cytotoxic, Antiproliferative, and Antineoplastic Effects

The marine environment is highly diverse, each living creature fighting to establish and proliferate. Among marine organisms, cyanobacteria are astounding secondary metabolite producers representing a wonderful source of biologically active molecules aimed to communicate, defend from predators, or compete. Studies on these molecules’ origins and activities have been systematic, although much is still to be discovered. Their broad chemical diversity results from integrating peptide and polyketide synthetases and synthases, along with cascades of biosynthetic transformations resulting in new chemical structures. Cyanobacteria are glycolipid, macrolide, peptide, and polyketide producers, and to date, hundreds of these molecules have been isolated and tested. Many of these compounds have demonstrated important bioactivities such as cytotoxicity, antineoplastic, and antiproliferative activity with potential pharmacological uses. Some are currently under clinical investigation. Additionally, conventional chemotherapeutic treatments include drugs with a well-known range of side effects, making anticancer drug research from new sources, such as marine cyanobacteria, necessary. This review is focused on the anticancer bioactivities of metabolites produced by marine cyanobacteria, emphasizing the identification of each variant of the metabolite family, their chemical structures, and the mechanisms of action underlying their biological and pharmacological activities.

Voltage-Gated Sodium Channels: A Prominent Target of Marine Toxins

Voltage-gated sodium channels (VGSCs) are considered to be one of the most important ion channels given their remarkable physiological role. VGSCs constitute a family of large transmembrane proteins that allow transmission, generation, and propagation of action potentials. This occurs by conducting Na⁺ ions through the membrane, supporting cell excitability and communication signals in various systems. As a result, a wide range of coordination and physiological functions, from locomotion to cognition, can be accomplished. Drugs that target and alter the molecular mechanism of VGSCs’ function have highly contributed to the discovery and perception of the function and the structure of this channel. Among those drugs are various marine toxins produced by harmful microorganisms or venomous animals. These toxins have played a key role in understanding the mode of action of VGSCs and in mapping their various allosteric binding sites. Furthermore, marine toxins appear to be an emerging source of therapeutic tools that can relieve pain or treat VGSC-related human channelopathies. Several studies documented the effect of marine toxins on VGSCs as well as their pharmaceutical applications, but none of them underlined the principal marine toxins and their effect on VGSCs. Therefore, this review aims to highlight the neurotoxins produced by marine animals such as pufferfish, shellfish, sea anemone, and cone snail that are active on VGSCs and discuss their pharmaceutical values.

Neosaxitoxin Inhibits the Expression of Inflammation Markers of the M1 Phenotype in Macrophages

(1) Background: Neosaxitoxin (NeoSTX) has been used as a local anesthetic, but its anti-inflammatory effects have not been well defined. In the present study, we investigate the effects of NeoSTX on lipopolysaccharide (LPS)-activated macrophages. (2) Methods: Raw 264.7 and equine PBMC cells were incubated with or without 100 ng/mL LPS in the presence or absence of NeoSTX (1µM). The expression of inflammatory mediators was assessed: nitric oxide (NO) content using the Griess assay, TNF-α content using the ELISA assay, and mRNA of inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) using a real-time polymerase chain reaction. (3) Results: NeoSTX (1 μM) significantly inhibited the release of NO, TNF-α, and expression of iNOS, IL-1β, and TNF-α in LPS-activated macrophages of both species studied. Furthermore, our study shows that the LPS-induced release of inflammatory mediators was suppressed by NeoSTX. Additionally, NeoSTX deactivated polarized macrophages to M1 by LPS without compromising its polarization towards M2. (4) Conclusions: NeoSTX inhibits LPS-induced release of inflammatory mediators from macrophages, and these effects may be mediated by the blockade of voltage-gated sodium channels (VGSC).

Paralytic Shellfish Toxins (PST)-Transforming Enzymes: A Review

Paralytic shellfish toxins (PSTs) are a group of toxins that cause paralytic shellfish poisoning through blockage of voltage-gated sodium channels. PSTs are produced by prokaryotic freshwater cyanobacteria and eukaryotic marine dinoflagellates. Proliferation of toxic algae species can lead to harmful algal blooms, during which seafood accumulate high levels of PSTs, posing a health threat to consumers. The existence of PST-transforming enzymes was first remarked due to the divergence of PST profiles and concentrations between contaminated bivalves and toxigenic organisms. Later, several enzymes involved in PST transformation, synthesis and elimination have been identified. The knowledge of PST-transforming enzymes is necessary for understanding the processes of toxin accumulation and depuration in mollusk bivalves. Furthermore, PST-transforming enzymes facilitate the obtainment of pure analogues of toxins as in natural sources they are present in a mixture. Pure compounds are of interest for the development of drug candidates and as analytical reference materials. PST-transforming enzymes can also be employed for the development of analytical tools for toxin detection. This review summarizes the PST-transforming enzymes identified so far in living organisms from bacteria to humans, with special emphasis on bivalves, cyanobacteria and dinoflagellates, and discusses enzymes' biological functions and potential practical applications.

Marine Toxins and Nociception: Potential Therapeutic Use in the Treatment of Visceral Pain Associated with Gastrointestinal Disorders

Visceral pain, of which the pathogenic basis is currently largely unknown, is a hallmark symptom of both functional disorders, such as irritable bowel syndrome, and inflammatory bowel disease. Intrinsic sensory neurons in the enteric nervous system and afferent sensory neurons of the dorsal root ganglia, connecting with the central nervous system, represent the primary neuronal pathways transducing gut visceral pain. Current pharmacological therapies have several limitations, owing to their partial efficacy and the generation of severe adverse effects. Numerous cellular targets of visceral nociception have been recognized, including, among others, channels (i.e., voltage-gated sodium channels, VGSCs, voltage-gated calcium channels, VGCCs, Transient Receptor Potential, TRP, and Acid-sensing ion channels, ASICs) and neurotransmitter pathways (i.e., GABAergic pathways), which represent attractive targets for the discovery of novel drugs. Natural biologically active compounds, such as marine toxins, able to bind with high affinity and selectivity to different visceral pain molecular mediators, may represent a useful tool (1) to improve our knowledge of the physiological and pathological relevance of each nociceptive target, and (2) to discover therapeutically valuable molecules. In this review we report the most recent literature describing the effects of marine toxin on gastrointestinal visceral pain pathways and the possible clinical implications in the treatment of chronic pain associated with gut diseases.

Neurobiology and therapeutic utility of neurotoxins targeting postsynaptic mechanisms of neuromuscular transmission

The neuromuscular junction (NMJ) is the principal site for the translation of motor neurochemical signals to muscle activity. Therefore, the release and sensing machinery of acetylcholine (ACh) along with muscle contraction are two of the main targets of natural toxins and pathogens, causing paralysis. Given pharmacology and medical advances, the active ingredients of toxins that target postsynaptic mechanisms have become of major interest, showing promise as drug leads. Herein, we review key facets of prevalent toxins modulating the mechanisms of ACh sensing and generation of the postsynaptic response, with muscle contraction. We consider the correlation between their outstanding selectivity and potency plus effects on motor function, and discuss emerging data advocating their usage for the development of therapies alleviating neuromuscular dysfunction.

Biocatalytic Detoxification of Paralytic Shellfish Toxins

Small molecules that bind to voltage-gated sodium channels (VGSCs) are promising leads in the treatment of numerous neurodegenerative diseases and pain. Nature is a highly skilled medicinal chemist in this regard, designing potent VGSC ligands capable of binding to and blocking the channel, thereby offering compounds of potential therapeutic interest. Paralytic shellfish toxins (PSTs), produced by cyanobacteria and marine dinoflagellates, are examples of these naturally occurring small molecule VGSC blockers that can potentially be leveraged to solve human health concerns. Unfortunately, the remarkable potency of these natural products results in equally exceptional toxicity, presenting a significant challenge for the therapeutic application of these compounds. Identifying less potent analogs and convenient methods for accessing them therefore provides an attractive approach to developing molecules with enhanced therapeutic potential. Fortunately, Nature has evolved tools to modulate the toxicity of PSTs through selective hydroxylation, sulfation, and desulfation of the core scaffold. Here, we demonstrate the function of enzymes encoded in cyanobacterial PST biosynthetic gene clusters that have evolved specifically for the sulfation of highly functionalized PSTs, the substrate scope of these enzymes, and elucidate the biosynthetic route from saxitoxin to monosulfated gonyautoxins and disulfated C-toxins. Finally, the binding affinities of the nonsulfated, monosulfated, and disulfated products of these enzymatic reactions have been evaluated for VGSC binding affinity using mouse whole brain membrane preparations to provide an assessment of relative toxicity. These data demonstrate the unique detoxification effect of sulfotransferases in PST biosynthesis, providing a potential mechanism for the development of more attractive PST-derived therapeutic analogs.

Long-lasting, reversible and non-neurotoxic inactivation of hippocampus activity induced by neosaxitoxin

BACKGROUND

Neosaxitoxin (NeoSTX) and related paralytics shellfish toxins has been successfully used as local anesthetic and muscle relaxants to treat a variety of ailments. The primary mechanism of action of these toxins occurs by blocking voltage-gated sodium channels with compounds such as TTX, lidocaine, or derivatives. However, most of these non-classical sodium channel blockers act with a reduced time effect as well as ensuing neurotoxicity.

NEW METHOD

In this report, we show that the use of local NeoSTX injections inactivates the hippocampal neuronal activity reversibly with a by long-term dynamics, without neuronal damage.

RESULTS

A single 10 ng/μl injection of NeoSTX in the dorsal CA1 region abolished for up to 48 h memory capacities and neuronal activity measured by the neuronal marker c-fos. After 72 h of toxin injection, the animals fully recover their memory capacities and hippocampal neuronal activity. The histological inspection of NeoSTX injected brain regions revealed no damage to the tissue or reactive gliosis, similar to vehicle injection. Acute electrophysiological recording in vivo shows, also, minimal spreading of the NeoSTX in the cerebral tissue.

COMPARISON WITH EXISTING METHODS

Intracerebral NeoSTX injection showed longer effects than other voltage sodium channel blocker, with minimal spreading and no neuronal damage.

CONCLUSION

NeoSTX is a new useful tool that reversibly inactivates different brains region for a long time, with minimal diffusion and without neuronal damage. Moreover, NeoSTX can be used as a valuable sodium channel blocker for many studies in vivo and with potential therapeutic uses.

Guanidinium Toxins and Their Interactions with Voltage-Gated Sodium Ion Channels

Guanidinium toxins, such as saxitoxin (STX), tetrodotoxin (TTX) and their analogs, are naturally occurring alkaloids with divergent evolutionary origins and biogeographical distribution, but which share the common chemical feature of guanidinium moieties. These guanidinium groups confer high biological activity with high affinity and ion flux blockage capacity for voltage-gated sodium channels (NaV). Members of the STX group, known collectively as paralytic shellfish toxins (PSTs), are produced among three genera of marine dinoflagellates and about a dozen genera of primarily freshwater or brackish water cyanobacteria. In contrast, toxins of the TTX group occur mainly in macrozoa, particularly among puffer fish, several species of marine invertebrates and a few terrestrial amphibians. In the case of TTX and analogs, most evidence suggests that symbiotic bacteria are the origin of the toxins, although endogenous biosynthesis independent from bacteria has not been excluded. The evolutionary origin of the biosynthetic genes for STX and analogs in dinoflagellates and cyanobacteria remains elusive. These highly potent molecules have been the subject of intensive research since the latter half of the past century; first to study the mode of action of their toxigenicity, and later as tools to characterize the role and structure of NaV channels, and finally as therapeutics. Their pharmacological activities have provided encouragement for their use as therapeutants for ion channel-related pathologies, such as pain control. The functional role in aquatic and terrestrial ecosystems for both groups of toxins is unproven, although plausible mechanisms of ion channel regulation and chemical defense are often invoked. Molecular approaches and the development of improved detection methods will yield deeper understanding of their physiological and ecological roles. This knowledge will facilitate their further biotechnological exploitation and point the way towards development of pharmaceuticals and therapeutic applications.