Anti-nociceptive effects induced by intrathecal injection of BmK AS, a polypeptide from the venom of Chinese-scorpion Buthus martensi Karsch, in rat formalin test

Spider and scorpion knottins targeting voltage-gated sodium ion channels in pain signaling

In sensory neurons that transmit pain signals, whether acute or chronic, voltage-gated sodium channels (VGSCs) are crucial for regulating excitability. NaV1.1, NaV1.3, NaV1.6, NaV1.7, NaV1.8, and NaV1.9 have been demonstrated and defined their functional roles in pain signaling based on their biophysical properties and distinct patterns of expression in each subtype of sensory neurons. Scorpions and spiders are traditional Chinese medicinal materials, belonging to the arachnid class. Most of the studied species of them have evolved venom peptides that exhibit a wide variety of knottins specifically targeting VGSCs with subtype selectivity and conformational specificity. This review provides an overview on the exquisite knottins from scorpion and spider venoms targeting pain-related NaV channels, describing the sequences and the structural features as well as molecular determinants that influence their selectivity on special subtype and at particular conformation, with an aim for the development of novel research tools on NaV channels and analgesics with minimal adverse effects.

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.

The Pivotal Potentials of Scorpion Buthus Martensii Karsch-Analgesic-Antitumor Peptide in Pain Management and Cancer

Scorpion Buthus martensii Karsch -analgesic-antitumor peptide (BmK AGAP) has been used to treat diseases like tetanus, tuberculosis, apoplexy, epilepsy, spasm, migraine headaches, rheumatic pain, and cancer in China. AGAP is a distinctive long-chain scorpion toxin with a molecular mass of 7142 Da and composed of 66 amino acids cross-linked by four disulfide bridges. Voltage-gated sodium channels (VGSCs) are present in excitable membranes and partakes in essential roles in action potentials generation as compared to the significant function of voltage-gated calcium channels (VGCCs). A total of nine genes (Nav1.1-Nav1.9) have been recognized to encode practical sodium channel isoforms. Nav1.3, Nav1.7, Nav1.8, and Nav1.9 have been recognized as potential targets for analgesics. Nav1.8 and Nav1.9 are associated with nociception initiated by inflammation signals in the neuronal pain pathway, while Nav1.8 is fundamental for neuropathic pain at low temperatures. AGAP has a sturdy inhibitory influence on both viscera and soma pain. AGAP potentiates the effects of MAPK inhibitors on neuropathic as well as inflammation-associated pain. AGAP downregulates the secretion of phosphorylated p38, phosphorylated JNK, and phosphorylated ERK 1/2 in vitro. AGAP has an analgesic activity which may be an effective therapeutic agent for pain management because of its downregulation of PTX3 via NF-κB and Wnt/beta-catenin signaling pathway. In cancers like colon cancer, breast cancer, lymphoma, and glioma, rAGAP was capable of blocking the proliferation. Thus, AGAP is a promising therapy for these tumors. Nevertheless, research is needed with other tumors.

Peptides with therapeutic potential in the venom of the scorpion Buthus martensii Karsch

The scorpion Buthus martensii Karsch (BmK) has generated significant interest due to the presence of biologically active peptides in its venom. In the past decade, dozens of different peptides from BmK have been identified. Most of the peptides are neurotoxins and are responsible for the toxicity of BmK venom. Other peptides, including neurotoxins and non-disulfide-bridged peptides, show potential anticancer, antimicrobial, analgesic, and anti-epileptic therapeutic effects. These peptides are attractive candidates for drug development, and peptide derivatives have also been designed to enhance their therapeutic potential, such as ADWX-1 and Kn2-7. In this review, we provide an overview of the most promising peptides found in BmK venom and of modified peptide derivatives showing therapeutic potential.

Inhibition of spinal MAPKs by scorpion venom peptide BmK AGAP produces a sensory-specific analgesic effect

Background

Several studies have shown that scorpion venom peptide BmK AGAP has an analgesic activity. Our previous study also demonstrated that intraplantar injection of BmK AGAP ameliorates formalin-induced spontaneous nociceptive behavior. However, the effect of intrathecal injection of BmK AGAP on nociceptive processing is poorly understood.

Methods

We investigated the effects of intrathecal injection of BmK AGAP on spinal nociceptive processing induced by chronic constrictive injury or formalin. Thermal hyperalgesia and mechanical allodynia were measured using radiant heat and the von Frey filaments test. Formalin-induced spontaneous nociceptive behavior was also investigated. C-Fos expression was assessed by immunohistochemistry. Phosphorylated mitogen-activated protein kinase (p-MAPK) expression was monitored by Western blot assay.

Results

Intrathecal injection of BmK AGAP reduced chronic constrictive injury-induced neuropathic pain behavior and pain from formalin-induced inflammation, accompanied by decreased expression of spinal p-MAPKs and c-Fos protein. The results of combining low doses of different MAPK inhibitor (U0126, SP600125, or SB203580; 0.1 µg for each inhibitor) with a low dose of BmK AGAP (0.2 µg) suggested that BmK AGAP could potentiate the effects of MAPK inhibitors on inflammation-associated pain.

Conclusion

Our results demonstrate that intrathecal injection of BmK AGAP produces a sensory-specific analgesic effect via a p-MAPK-dependent mechanism.

BotAF, a new Buthus occitanus tunetanus scorpion toxin, produces potent analgesia in rodents

This work reports the purification of new potent scorpion neuropeptide, named BotAF, by an activity-guided screening approach. BotAF is a 64-residue long-chain peptide that shares very high similarity with the original β-like scorpion toxin group, in which several peptides have been characterized to be anti-nociceptive in rodents. BotAF administration to rodents does not produce any toxicity or motor impairment, including at high doses. In all models investigated, BotAF turned out to be an efficient peptide in abolishing acute and inflammatory (both somatic and visceral) pain in rodents. It performs with high potency compared to standard analgesics tested in the same conditions. The anti-nociceptive activity of BotAF depends on the route of injection: it is inactive when tested by i.c.v. or i.v. routes but gains in potency when pre-injected locally (in the same compartment than the irritant itself) or by i.t. root 40 to 60 min before pain induction, respectively. BotAF is not an AINS-like compound as it fails to reduce inflammatory edema. Also, it does not activate the opioidergic system as its activity is not affected by naloxone. BotAF does also not bind onto RyR and has low activity towards DRG ion channels (particularly TTX sensitive Na⁺ channels) and does not bind onto rat brain synaptosome receptors. In somatic and visceral pain models, BotAF dose-dependently inhibited lumbar spinal cord c-fos/c-jun mRNA up regulation. Altogether, our data favor a spinal or peripheral anti-nociceptive mode of action of BotAF.

Anti-inflammatory and Analgesic Effects of Polygonum orientale L. Extracts

Background and Purpose:Polygonum orientale L. (family: Polygonaceae), named Hongcao in China, is a Traditional Chinese Medicinal and has long been used for rheumatic arthralgia and rheumatoid arthritis. However, no pharmacological and mechanism study to confirm these clinic effects have been published. In this investigation, the anti-inflammatory, analgesic effects and representative active ingredient compounds of P. orientale have been studied. Methods: Dried small pieces of the stems and leaves of P. orientale were decocted with water and partitioned successively to obtain ethyl acetate and ethyl ether extract of P. orientale (POEa and POEe). Chemical compositions of them were analyzed by UPLC-Q-Exactive HRMS. Anti-inflammatory and analgesic effects of POEa and POEe were evaluated using xylene induced ear edema, carrageenan induced paw edema, Freunds' complete adjuvant induced arthritis, and formaldehyde induced pain in rat. Their mechanisms of anti-inflammatory and analgesic effects were also studied via assays of TNF-α, IL-1β, IL-6, and PGE2 in serum. Results: UPLC-Q-Exactive HRMS analysis showed that POEa and POEe mainly contained flavonoids including orientin, isoorientin, vitexin, luteolin, and quercetin. Furthermore, anti-inflammatory effects of POEa and POEe were evident in xylene induced ear edema. The paw edema in Freund's complete adjuvant and carrageenan were significantly (P < 0.05, 0.01) inhibited by POEa (5, 7.5 g/kg). POEe (7.5 g/kg) was significantly (P < 0.05, 0.01) inhibited Freunds' complete adjuvant induced paw edema and cotton pellet induced granuloma formation. Similarly, POEe significantly (P < 0.05, 0.01) inhibited the pain sensation in acetic acid induced writhing test. POEa (5, 7.5 g/kg) significantly (P < 0.05, 0.01) inhibited formaldehyde induced pain in both phases. POEa (7.5 g/kg) markedly (P < 0.05) prolonged the latency period of hot plate test after 30 and 60 min. The concentrations of TNF-α, IL-1β, IL-6, and PGE2 were significantly (P < 0.01) decreased by POEa (3.75, 5 g/kg). Conclusion: POEa and POEe have anti-inflammatory and analgesic effects, which was mainly relevant to the presence of flavonoids, including orientin, isoorientin, vitexin, luteolin, and quercetin. The mechanism of anti-inflammatory and analgesic effects of POEa may be to decrease the concentrations of TNF-α, IL-1β, IL-6, and PGE2 in serum.

Fos Protein as a Marker of Neuronal Activity: a Useful Tool in the Study of the Mechanism of Action of Natural Products with Analgesic Activity

Pain treatment is still ineffective in many conditions and remains one of the greatest challenges of modern medicine. Historically, due to the incredible variety of pharmacologically promising natural products (NPs) and the chemical complexity of their compounds, scientists have explored their use as a source of treatment for diseases or symptomatology. Fos protein and its precursor, the gene c-Fos, have been the subject of study in relation to the pathophysiology of pain as a possible tool to aid in its understanding. More recently, it has become a useful tool in the study of NPs with analgesic profile. Thus, this systematic review aimed to investigate the analgesic effect of NPs and derivatives through changes in Fos protein or c-Fos expression in nervous system central. The search terms "analgesics," "Fos," and "drug effects" were used in the databases PubMed, MEDLINE, Scopus, and Embase. Forty-six articles were identified. Twenty-five articles investigated Fos expression in the spinal cord, 1 in dorsal root ganglion, 11 in brain areas, and 9 investigated the association between the spinal cord and brain areas. Although Fos protein expression has been used as a tool in the studies of the mechanism of action of pain in relation to NPs with analgesic activity, the associations between brain areas and the spinal cord-and the possible pathways involved-have not yet been fully elucidated and deserve further study.

Functional up-regulation of Nav1.8 sodium channel on dorsal root ganglia neurons contributes to the induction of scorpion sting pain

BmK I, purified from the venom of scorpion Buthus martensi Karsch (BmK), is a receptor site-3-specific modulator of voltage-gated sodium channels (VGSCs) and can induce pain-related behaviors in rats. The tetrodotoxin-resistant (TTX-R) sodium channel Nav1.8 contributes to most of the sodium current underlying the action potential upstroke in dorsal root ganglia (DRG) neurons and may serve as a critical ion channel targeted by BmK I. Herein, using electrophysiological, molecular, and behavioral approaches, we investigated whether the aberrant expression of Nav1.8 in DRG contributes to generation of pain induced by BmK I. The expression of Nav1.8 was found to be significantly increased at both mRNA and protein levels following intraplantar injection of BmK I in rats. In addition, the current density of TTX-R Nav1.8 sodium channel is significantly increased and the gating kinetics of Nav1.8 is also altered in DRG neurons from BmK I-treated rats. Furthermore, spontaneous pain and mechanical allodynia, but not thermal hyperalgesia induced by BmK I, are significantly alleviated through either blockade of the Nav1.8 sodium channel by its selective blocker A-803467 or knockdown of the Nav1.8 expression in DRG by antisense oligodeoxynucleotide (AS-ODN) targeting Nav1.8 in rats. Finally, BmK I was shown to induce enhanced pain behaviors in complete freund's adjuvant (CFA)-inflamed rats, which was partly due to the over-expression of Nav1.8 in DRG. Our results suggest that functional up-regulation of Nav1.8 channel on DRG neurons contributes to the development of BmK I-induced pain in rats.

Mast Cell-Mediated Mechanisms of Nociception

Mast cells are tissue-resident immune cells that release immuno-modulators, chemo-attractants, vasoactive compounds, neuropeptides and growth factors in response to allergens and pathogens constituting a first line of host defense. The neuroimmune interface of immune cells modulating synaptic responses has been of increasing interest, and mast cells have been proposed as key players in orchestrating inflammation-associated pain pathobiology due to their proximity to both vasculature and nerve fibers. Molecular underpinnings of mast cell-mediated pain can be disease-specific. Understanding such mechanisms is critical for developing disease-specific targeted therapeutics to improve analgesic outcomes. We review molecular mechanisms that may contribute to nociception in a disease-specific manner.

Beneficial effects of Androctonus australis hector venom and its non-toxic fraction in the restoration of early hepatocyte-carcinogenesis induced by FB1 mycotoxin: Involvement of oxidative biomarkers

Some venom components are known to present potential biological activities that are useful as tools in therapeutics. In this study anti-tumoral activity of Androctonus australis hector (Aah) venom and its purified fraction on early step of hepato-carcinogenesis initiated by Fumonisin (FB1), was tested. Initiated hepatic tumor was assessed in mice by decreased doses of Fumonisin B1 associated to phenobarbital. Scorpion venom was used to investigate its activity on initiated tumor by FB1. Evaluation of oxidative unbalance, enzymatic activities and DNA quantification in the liver were correlated with tissue analysis. Obtained results showed that the initiated pathogenesis by FB1 at seven months was characterized by tissue alterations and biomarker variations. These alterations were characterized by atypical lesions such as muffled nucleus, karyo- and cyto-megaly; up normal and large number of nuclei into hepatocytes. These alterations were confirmed by DNA alteration. An unbalance of oxidative status was also observed, characterized by an increased levels of respectively oxidant (NO and MDA) and antioxidant (GSH and catalase activity) mediators. Aah venom and its non-toxic fraction used at low doses seemed to be able to restore partially the hepatic altered tissue induced by FB1. Decreased levels of oxidative and anti-oxidative mediators were also observed. DNA in hepatocytes returned also to the physiological values. Structure of hepatic tissue showed restoration of some alterations such as karyo- and cyto-megaly; decrease of polyploidy hepatocytes induced by FB1. Aah venom and its non-toxic fraction seem to contain some bioactive components with anti-tumoral activity. Purification of this activity from non-toxic fraction F1 could be of interest to identify the components with anti-tumoral activities.

Cloning and molecular characterization of scorpion Buthus martensi venom hyaluronidases: a novel full-length and diversiform noncoding isoforms

Hyaluronidase is a common component of scorpion venom and has been considered as "spreading factor" that promotes a fast penetration of the venom in the anaphylactic reaction. In the current study, a novel full-length of hyaluronidase BmHYI and three noncoding isoforms of BmHYII, BmHYIII and BmHYIV were cloned by using a combined strategy based on peptide sequencing and Rapid Amplification of cDNA Ends (RACE). BmHYI has 410 amino acid residues containing the catalytic, positional and five potential N-glycosylation sites. The deduced protein sequence of BmHYI shares significant identity with venom hyaluronidases from bees and snakes. The phylogenetic analysis showed early divergence and independent evolution of BmHYI from other hyaluronidases. An extraordinarily high level of sequence similarity was detected among four sequences. But, BmHYII, BmHYIII and BmHYIV were short of stop-codon in the open reading frame and poly(A) signal in the 3' end.

Pharmacological kinetics of BmK AS, a sodium channel site 4-specific modulator on Nav1.3

OBJECTIVE

In this study, the pharmacological kinetics of Buthus martensi Karsch (BmK) AS, a specific modulator of voltage-gated sodium channel site 4, was investigated on Na(v)1.3 expressed in Xenopus oocytes.

METHODS

Two-electrode voltage clamp was used to record the whole-cell sodium current.

RESULTS

The peak currents of Na(v)1.3 were depressed by BmK AS over a wide range of concentrations (10, 100, and 500 nmol/L). Most remarkably, BmK AS at 100 nmol/L hyperpolarized the voltage-dependence and increased the voltage-sensitivity of steady-state activation/inactivation. In addition, BmK AS was capable of hyperpolarizing not only the fast inactivation but also the slow inactivation, with a greater preference for the latter. Moreover, BmK AS accelerated the time constant and increased the ratio of recovery in Na(v)1.3 at all concentrations.

CONCLUSION

This study provides direct evidence that BmK AS facilitates steady-state activation and inhibits slow inactivation by stabilizing both the closed and open states of the Na(v)1.3 channel, which might result from an integrative binding to two receptor sites on the voltage-gated sodium channels. These results may shed light on therapeutics against Na(v)1.3-targeted pathology.

PKA phosphorylation reshapes the pharmacological kinetics of BmK AS, a unique site-4 sodium channel-specific modulator

Although modulation of the activity of voltage-gated sodium channels (VGSCs) by protein kinase A (PKA) phosphorylation has been investigated in multiple preparations, the pharmacological sensitivity of VGSCs to scorpion toxins after PKA phosphorylation has rarely been approached. In this study, the effects of BmK AS, a sodium channel-specific modulator from Chinese scorpion Buthus martensi Karsch, on the voltage-dependent activation and inactivation of Nav1.2 were examined before and after PKA activation. After PKA phosphorylation, the pattern of dose-dependent modulation of BmK AS, on both Nav1.2α and Nav1.2 (α + β1) was reshaped. Meanwhile, the shifts in voltage-dependency of activation and inactivation induced by BmK AS were attenuated. The results suggested that PKA might play a role in different patterns how β-like toxins such as BmK AS modulate gating properties and peak currents of VGSCs.

Antinociceptive effects of analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch, on formalin-induced inflammatory pain through a mitogen-activated protein kinases-dependent mechanism in mice

In the present study, we investigated the anti-nociceptive effect and the underlying mechanism of the analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch. AGAP in doses of 0.2, 1 and 5 µg was injected intraplantarly (i.pl.) before formalin injection 10 min at the same site. The suppression by intraplantar injection of AGAP on formalin-induced spontaneous nociceptive behaviors was investigated. The results show that AGAP could dose-dependently inhibit formalin-induced two-phase spontaneous flinching response. To investigate the mechanism of action of treatment with AGAP in inflammatory pain, the expressions of peripheral and spinal phosphorylated mitogen-activated protein kinases (phospho-MAPKs) including p-p38, p-ERK and p-JNK were examined. We found that formalin increased the expressions of peripheral and spinal MAPKs, which were prevented by pre-intraplantar injection of AGAP in inflammation pain model in mice. AGAP could also decrease the expression of spinal Fos induced by formalin. Furthermore, combinations the lower doses of the inhibitors of MAPKs (U0126, SP600125, or SB203580 0.1 µg) with the lower dose of AGAP (0.2 µg), the results suggested that AGAP could potentiate the effects of the inhibitors of MAPKs on the inflammatory pain. The present results indicate that pre-intraplantar injection of AGAP prevents the inflammatory pain induced by formalin through a MAPKs-mediated mechanism in mice.

Different types of toxins targeting TRPV1 in pain

The transient receptor potential vanilloid 1(TRPV1) channels are members of the transient receptor potential (TRP) superfamily. Members of this family are expressed in primary sensory neurons and are best known for their role in nociception and sensory transmission. Multiple painful stimuli can activate these channels. In this review, we discussed the mechanisms of different types of venoms that target TRPV1, such as scorpion venom, botulinum neurotoxin, spider toxin, ciguatera fish poisoning (CFP) and neurotoxic shellfish poisoning (NSP). Some of these toxins activate TRPV1; however, some do not. Regardless of TRPV1 inhibition or activation, they occur through different pathways. For example, BoNT/A decreases TRPV1 expression levels by blocking TRPV1 trafficking to the plasma membrane, although the exact mechanism is still under debate. Vanillotoxins from tarantula (Psalmopoeus cambridgei) are proposed to activate TRPV1 via interaction with a region of TRPV1 that is homologous to voltage-dependent ion channels. Here, we offer a description of the present state of knowledge for this complex subject.

Scorpion β-toxin interference with NaV channel voltage sensor gives rise to excitatory and depressant modes

Scorpion β toxins, peptides of ∼70 residues, specifically target voltage-gated sodium (Na_V) channels to cause use-dependent subthreshold channel openings via a voltage–sensor trapping mechanism. This excitatory action is often overlaid by a not yet understood depressant mode in which Na_V channel activity is inhibited. Here, we analyzed these two modes of gating modification by β-toxin Tz1 from Tityus zulianus on heterologously expressed Na_V1.4 and Na_V1.5 channels using the whole cell patch-clamp method. Tz1 facilitated the opening of Na_V1.4 in a use-dependent manner and inhibited channel opening with a reversed use dependence. In contrast, the opening of Na_V1.5 was exclusively inhibited without noticeable use dependence. Using chimeras of Na_V1.4 and Na_V1.5 channels, we demonstrated that gating modification by Tz1 depends on the specific structure of the voltage sensor in domain 2. Although residue G658 in Na_V1.4 promotes the use-dependent transitions between Tz1 modification phenotypes, the equivalent residue in Na_V1.5, N803, abolishes them. Gating charge neutralizations in the Na_V1.4 domain 2 voltage sensor identified arginine residues at positions 663 and 669 as crucial for the outward and inward movement of this sensor, respectively. Our data support a model in which Tz1 can stabilize two conformations of the domain 2 voltage sensor: a preactivated outward position leading to Na_V channels that open at subthreshold potentials, and a deactivated inward position preventing channels from opening. The results are best explained by a two-state voltage–sensor trapping model in that bound scorpion β toxin slows the activation as well as the deactivation kinetics of the voltage sensor in domain 2.

U-shaped dose-dependent effects of BmK AS, a unique scorpion polypeptide toxin, on voltage-gated sodium channels

BACKGROUND AND PURPOSE

Buthus martensi Karsch (BmK) AS is a scorpion polypeptide toxin, said to target the voltage-gated sodium channels (VGSCs). However, the mechanism of action of BmK AS on the VGSCs has yet to be defined.

EXPERIMENTAL APPROACH

We examined the electrophysiological effects of BmK AS in a wide dose range on the rat brain-type VGSC alpha-subunit, rNav1.2a, heterologously expressed in Xenopus oocytes and on the VGSCs endogenously expressed in the dorsal root ganglion neuroblastoma ND7-23 cell line.

KEY RESULTS

In the oocytes, BmK AS depolarized the voltage dependence of activation and inactivation of rNav1.2a at 0.1 and 500 nM whereas these parameters were hyperpolarized at 1 nM. In ND7-23 cells, BmK AS hyperpolarized the voltage dependence of activation and inactivation at 0.1, 1 and 100 nM but not 10 nM. BmK AS also hyperpolarized the voltage dependence of recovery from inactivation at 0.1 and 100 nM and slowed the recovery kinetics at all concentrations, but the effects of 1 and 10 nM were relatively smaller than those at 0.1 and 100 nM. Moreover, the inactivation of VGSCs was potentiated by 10 nM BmK AS in both systems, whereas it was inhibited by 0.1 or 100 nM BmK AS in the oocytes or ND7-23 cells respectively.

CONCLUSIONS AND IMPLICATIONS

BmK AS modulated the VGSCs in a unique U-shaped dose-dependent manner, which could be due to the opposing effects of binding to two distinct receptor sites on the VGSCs.