Molecular characterization of an anti-epilepsy peptide from the scorpion Buthus martensi Karsch

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.

Scorpion venom heat-resistant synthesized peptide ameliorates 6-OHDA-induced neurotoxicity and neuroinflammation: likely role of Nav 1.6 inhibition in microglia

BACKGROUND AND PURPOSE

Microglia-related inflammation is associated with the pathology of Parkinson's disease. Functional voltage-gated sodium channels (VGSCs) are involved in regulating microglial function. Here, we aim to investigate the effects of scorpion venom heat-resistant synthesized peptide (SVHRSP) on 6-hydroxydopamine (6-OHDA)-induced Parkinson's disease-like mouse model and reveal its underlying mechanism.

EXPERIMENTAL APPROACH

Unilateral brain injection of 6-OHDA was performed to establish Parkinson's disease mouse model. After behaviour test, brain tissues were collected for morphological analysis and protein/gene expression examination. Primary microglia culture was used to investigate the role of sodium channel Na_v 1.6 in the regulation of microglia inflammation by SVHRSP.

KEY RESULTS

SVHRSP treatment attenuated motor deficits, dopamine neuron degeneration, activation of glial cells and expression of pro-inflammatory cytokines induced by 6-OHDA lesion. Primary microglia activation and the production of pro-inflammatory cytokines induced by lipopolysaccharide (LPS) were also suppressed by SVHRSP treatment. In addition, SVHRSP could inhibit mitogen-activated protein kinases (MAPKs) pathway, which plays pivotal roles in the pro-inflammatory response. Notably, SVHRSP treatment suppressed the overexpression of microglial Na_v 1.6 induced by 6-OHDA and LPS. Finally, it was shown that the anti-inflammatory effect of SVHRSP in microglia was Na_v 1.6 dependent and was related to suppression of sodium current and probably the consequent Na⁺ /Ca²⁺ exchange.

CONCLUSIONS AND IMPLICATIONS

SVHRSP might inhibit neuroinflammation and protect dopamine neurons via down-regulating microglial Na_v 1.6 and subsequently suppressing intracellular Ca²⁺ accumulation to attenuate the activation of MAPKs signalling pathway in microglia.

BmK AEP, an Anti-Epileptic Peptide Distinctly Affects the Gating of Brain Subtypes of Voltage-Gated Sodium Channels

BmK AEP, a scorpion peptide purified form the venom of Buthus martensii Karsch, has been reported to display anti-epileptic activity. Voltage-gated sodium channels (VGSCs) are responsible for the rising phase of action potentials (APs) in neurons and, therefore, controlling neuronal excitability. To elucidate the potential molecular mechanisms responsible for its anti-epileptic activity, we examined the influence of BmK AEP on AP firing in cortical neurons and how BmK AEP influences brain subtypes of VGSCs (Na_v1.1–1.3 and Na_v1.6). BmK AEP concentration-dependently suppresses neuronal excitability (AP firing) in primary cultured cortical neurons. Consistent with its inhibitory effect on AP generation, BmK AEP inhibits Na⁺ peak current in cortical neurons with an IC₅₀ value of 2.12 µM by shifting the half-maximal voltage of activation of VGSC to hyperpolarized direction by ~7.83 mV without affecting the steady-state inactivation. Similar to its action on Na⁺ currents in cortical neurons, BmK AEP concentration-dependently suppresses the Na⁺ currents of Na_v1.1, Na_v1.3, and Na_v1.6, which were heterologously expressed in HEK-293 cells, with IC₅₀ values of 3.20, 1.46, and 0.39 µM with maximum inhibition of 82%, 56%, and 93%, respectively. BmK AEP shifts the voltage-dependent activation in the hyperpolarized direction by ~15.60 mV, ~9.97 mV, and ~6.73 mV in Na_v1.1, Na_v1.3, and Na_v1.6, respectively, with minimal effect on steady-state inactivation. In contrast, BmK AEP minimally suppresses Na_v1.2 currents (~15%) but delays the inactivation of the channel with an IC₅₀ value of 1.69 µM. Considered together, these data demonstrate that BmK AEP is a relatively selective Na_v1.6 gating modifier which distinctly affects the gating of brain subtypes of VGSCs.

Chinese Medicine Protein and Peptide in Gene and Cell Therapy

The success of gene and cell therapy in clinic during the past two decades as well as our expanding ability to manipulate these biomaterials are leading to new therapeutic options for a wide range of inherited and acquired diseases. Combining conventional therapies with this emerging field is a promising strategy to treat those previously-thought untreatable diseases. Traditional Chinese medicine (TCM) has evolved for thousands of years in China and still plays an important role in human health. As part of the active ingredients of TCM, proteins and peptides have attracted long-term enthusiasm of researchers. More recently, they have been utilized in gene and cell therapy, resulting in promising novel strategies to treat both cancer and non-cancer diseases. This manuscript presents a critical review on this field, accompanied with perspectives on the challenges and new directions for future research in this emerging frontier.

Feeding recombinant E. coli with GST-mBmKTX fusion protein increases the fecundity and lifespan of Caenorhabditis elegans

Scorpion venom could be a useful treatment for a variety of diseases, such as cancer, epilepsy and analgesia. BmKTX is a polypeptide extracts from scorpion venom (PESV), which have attracted much attention from researchers in recent years. mBmKTX is a mutant polypeptide according to the amino acid sequence of BmKTX. We expressed it with the vector pGEX-4T-1 in Escherichia coli, and Caenorhabditis elegans were used as the animal model and fed with the strains. In this study, the expression of pGEX-mBmKTX was analyzed by SDS-PAGE, and GST-mBmKTX purified from pGEX-mBmKTX as a glutathione S-transferase (GST)-tagged fusion protein is approximately 30kDa. The secondary structure prediction shows that mBmKTX is mainly composed of approximately 13% β-sheet and 86% loop. A food clearance assay and brood size assay indicated that the worms fed pGEX-mBmKTX ate more and had greater fecundity than those fed the empty vector. A lifespan analysis demonstrated that mBmKTX could significantly prolong the lifespan of C. elegans, with an increase of 22.5% compared with the control. Behavioral assays confirmed that mBmKTX had no influence on the locomotion of C. elegans. In addition, microarray analysis and quantitative real-time PCR demonstrated that there are 320 differentially expressed genes, 182 of which are related to reproduction, growth and lifespan. In conclusion, the data suggested that mBmKTX has potential utility for increasing fecundity and animal survival.

Recombinant expression of Intrepicalcin from the scorpion Vaejovis intrepidus and its effect on skeletal ryanodine receptors

BACKGROUND

Scorpion venoms contain toxins that modulate ionic channels, among which are the calcins, a small group of short, basic peptides with an Inhibitor Cystine Knot (ICK) motif that target calcium release channels/ryanodine receptors (RyRs) with high affinity and selectivity. Here we describe the heterologous expression of Intrepicalcin, identified by transcriptomic analysis of venomous glands from Vaejovis intrepidus.

METHODS

Recombinant Intrepicalcin was obtained in Escherichia coli BL21-DE3 (periplasm) by fusing the Intrepicalcin gene to sequences coding for signal-peptide, thioredoxin, His-tag and enterokinase cleavage site.

RESULTS

[³H]Ryanodine binding, used as a functional index of RyR activity, revealed that recombinant Intrepicalcin activates skeletal RyR (RyR1) dose-dependently with K_d=17.4±4.0nM. Intrepicalcin significantly augments the bell-shaped [Ca²⁺]-[³H]ryanodine binding curve at all [Ca²⁺] ranges, as is characteristic of the calcins. In single channel recordings, Intrepicalcin induces the appearance of a subconductance state in RyR1 with a fractional value ∼55% of the full conductance state, very close to that of Vejocalcin. Furthermore, Intrepicalcin stimulates Ca²⁺ release at an initial dose=45.3±2.5nM, and depletes ~50% of Ca²⁺ load from skeletal sarcoplasmic reticulum vesicles.

CONCLUSIONS

We conclude that active recombinant Intrepicalcin was successfully obtained without the need of manual oxidation, enabling it to target RyR1s with high affinity.

GENERAL SIGNIFICANCE

This is the first calcin heterologously expressed in the periplasma of Escherichia coli BL21-DE3, shown to be pharmacologically effective, thus paving the way for the generation of Intrepicalcin variants that are required for structure-function relationship studies of calcins and RyRs.

Medical application of scorpion venom to breast cancer: A mini-review

Breast cancer is the leading cause of mortality in women worldwide. Today, 1 in 8 women born in the United States will have an invasive cancer in their lifetime. Despite significant attempts, the prognosis of metastatic breast cancer still remains poor. This has compelled scientists to look elsewhere for better therapeutic outcomes. Recent advances in venomic studies have demonstrated some promise in cancer-related ailments. Scorpion venom, a complex cocktail of biogenic amines, proteins, peptides, mucoproteins, organic salts and neurotoxins has shown a potential therapeutic application due to its cytotoxic, apoptogenic, immunosuppressive and antiproliferative properties. This communication reviews the effects of scorpion venom components on breast cancer and their mechanisms.

Venom Components of Iranian Scorpion Hemiscorpius lepturus Inhibit the Growth and Replication of Human Immunodeficiency Virus 1 (HIV-1)

Background:

During the recent years, significant progress has been achieved on development of novel anti-viral drugs. Natural products are assumed as the potential sources of novel anti-viral drugs; therefore, there are some previous studies reporting the anti-viral compounds from venomous animals. Based on the significant value for tracing of non-toxic anti-viral agents from natural resources, this study was aimed to investigate the anti-viral activity of some HPLC purified fractions derived from the venom of Iranian scorpion, Hemiscorpius lepturus, against human immunodeficiency virus 1 (HIV-1) and herpes simplex virus 1 (HSV-1).

Methods:

H. Lepturus crude venom was subjected to reverse phase HPLC analysis to determine its active components precisely where four dominant fractions obtained at retention time of 156-160 minutes. The phospholipase A2 and hemolytic activities of the purified fractions were first evaluated. Then the anti-viral activity was measured using single cycle HIV (NL4-3) replication and HSV (KOS) plaque reduction assays.

Results:

The H. lepturus crude venom inhibited HIV replication by 73% at the concentration of 200 µg/ml, while it did not show significant anti-HSV activity. It also inhibited the cell-free viral particles in a virucidal assay, while it showed no toxicity for the target cells in a proliferation assay. The four HPLC fractions purified from H. lepturus inhibited HIV with IC₅₀ of 20 µg/ml.

Conclusion:

H. lepturus venom contains components with considerable anti-HIV activity insofar as it has virucidal activity that offers a novel therapeutic approach against HIV infection. Our results suggest a promising pilot for anti-HIV drug discovery with H. lepturus scorpion venom.

In vitro and in vivo antitumor effects of the Egyptian scorpion Androctonus amoreuxi venom in an Ehrlich ascites tumor model

Scorpion venom is a highly complex mixture of about 100-700 different components, where peptides are the major constituents with various biological and pharmacological properties including anticancer activities. In this study, anticancer efficacy of the venom of the Egyptian scorpion Androctonus amoreuxi has been evaluated. In vitro, the human breast cancer MCF-7 cell line was treated with the venom and the IC50 was estimated. In vivo studies, Ehrlich ascites carcinoma (EAC) cells were inoculated into CD-1 mice intraperitoneally to form liquid tumor or subcutaneously to form solid tumor and then treated with intraperitoneal injection with venom (0.22 mg/kg) every other day. The total tumor cells in the ascitic fluid and the size of the solid tumor were assessed after 14 and 30 days, respectively. In addition, the mean survival time (MST), body weight, tumor volume, PCV, viability of tumor cells, CBC, AST, ALP, creatinine, oxidative stress biomarkers (GSH, MDA, PCC), tumor marker Ki67, growth factor VEGF and caspase-3 were measured in normal control, EAC control and venom-treated groups (n = 6). Treatment with venom induced anti-tumor effects against liquid and in solid tumors as indicated by a significant (P < 0.05) reduction in tumor volume/size, count of viable EAC cells, expression of Ki67 and VEGF as well as by remarkable increases in MST and caspase-3 expression as compared to non-treated group. Interestingly, the venom restored the altered hematological and biochemical parameters of tumor-bearing animals and significantly increased their life span. These data indicate to (1) the cytotoxic potential effects of A. amoreuxi on tumor cells via anti-proliferative, apoptotic and anti-angiogenic activities; (2) opening a new avenue for further studies on the anti-cancer effects of this agent.

Neuroactive compounds obtained from arthropod venoms as new therapeutic platforms for the treatment of neurological disorders

The impact of neurological disorders in society is growing with alarming estimations for an incidence increase in the next decades. These disorders are generally chronic and can affect individuals early during productive life, imposing real limitations on the performance of their social roles. Patients can have their independence, autonomy, freedom, self-image, and self-confidence affected. In spite of their availability, drugs for the treatment of these disorders are commonly associated with side effects, which can vary in frequency and severity. Currently, no effective cure is known. Nowadays, the biopharmaceutical research community widely recognizes arthropod venoms as a rich source of bioactive compounds, providing a plethora of possibilities for the discovery of new neuroactive compounds, opening up novel and attractive opportunities in this field. Several identified molecules with a neuropharmacological profile can act in the central nervous system on different neuronal targets, rendering them useful tools for the study of neurological disorders. In this context, this review aims to describe the current main compounds extracted from arthropod venoms for the treatment of five major existing neurological disorders: stroke, Alzheimer’s disease, epilepsy, Parkinson’s disease, and pathological anxiety.

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.

Scorpion venom heat-resistant peptide (SVHRP) enhances neurogenesis and neurite outgrowth of immature neurons in adult mice by up-regulating brain-derived neurotrophic factor (BDNF)

Scorpion venom heat-resistant peptide (SVHRP) is a component purified from Buthus martensii Karsch scorpion venom. Although scorpions and their venom have been used in Traditional Chinese Medicine (TCM) to treat chronic neurological disorders, the underlying mechanisms of these treatments remain unknown. We applied SVHRP in vitro and in vivo to understand its effects on the neurogenesis and maturation of adult immature neurons and explore associated molecular mechanisms. SVHRP administration increased the number of 5-bromo-2’-dexoxyuridine (BrdU)-positive cells, BrdU- positive/neuron-specific nuclear protein (NeuN)-positive neurons, and polysialylated-neural cell adhesion molecule (PSA-NCAM)-positive immature neurons in the subventricular zone (SVZ) and subgranular zone (SGZ) of hippocampus. Furthermore immature neurons incubated with SVHRP-pretreated astrocyte-conditioned medium exhibited significantly increased neurite length compared with those incubated with normal astrocyte-conditioned medium. This neurotrophic effect was further confirmed in vivo by detecting an increased average single area and whole area of immature neurons in the SGZ, SVZ and olfactory bulb (OB) in the adult mouse brain. In contrast to normal astrocyte-conditioned medium, higher concentrations of brain-derived neurotrophic factor (BDNF) but not nerve growth factor (NGF) or glial cell line-derived neurotrophic factor (GDNF) was detected in the conditioned medium of SVHRP-pretreated astrocytes, and blocking BDNF using anti-BDNF antibodies eliminated these SVHRP-dependent neurotrophic effects. In SVHRP treated mouse brain, more glial fibrillary acidic protein (GFAP)-positive cells were detected. Furthermore, immunohistochemistry revealed increased numbers of GFAP/BDNF double-positive cells, which agrees with the observed changes in the culture system. This paper describes novel effects of scorpion venom-originated peptide on the stem cells and suggests the potential therapeutic values of SVHRP.

Bioactive proteins and peptides isolated from Chinese medicines with pharmaceutical potential

Some protein pharmaceuticals from Chinese medicine have been developed to treat cardiovascular diseases, genetic diseases, and cancer. Bioactive proteins with various pharmacological properties have been successfully isolated from animals such as Hirudo medicinalis (medicinal leech), Eisenia fetida (earthworm), and Mesobuthus martensii (Chinese scorpion), and from herbal medicines derived from species such as Cordyceps militaris, Ganoderma, Momordica cochinchinensis, Viscum album, Poria cocos, Senna obtusifolia, Panax notoginseng, Smilax glabra, Ginkgo biloba, Dioscorea batatas, and Trichosanthes kirilowii. This article reviews the isolation methods, molecular characteristics, bioactivities, pharmacological properties, and potential uses of bioactive proteins originating from these Chinese medicines.

Purification, characterization, and bioactivity of a new analgesic-antitumor peptide from Chinese scorpion Buthus martensii Karsch

Scorpion venoms are complex mixtures of dozens or even hundreds of distinct proteins, many of which have diverse bioactivities. In this study, after bioassay-driven chromatographic purification, a new dual-function peptide with analgesic and antitumor activities was isolated and designated BmK AGAP-SYPU2. The first 12 amino acid residues were sequenced with Edman degradation. The cDNA was cloned by using rapid amplification of cDNA ends from the cDNA pool from scorpion glands. The amino acid sequence of BmK AGAP-SYPU2 was then deduced, and is consistent with the molecular mass measured with MALDI-TOF-MS. A preliminary pharmacological analysis revealed the following: in the dose-effect curve plotted with the mouse-twisting test, BmK AGAP-SYPU2 showed analgesic activity with an ED50 value of 1.42 mg/kg; in the time-effect curves plotted with a hot-plate procedure, BmK AGAP-SYPU2 had similar effects to those of the painkiller morphine, except for its longer duration. BmK AGAP-SYPU2 also showed antitumor activity against Ehrlich ascites tumor and S-180 fibrosarcoma models in vivo. Sequence alignment and homology modeling showed that BmK AGAP-SYPU2 is highly conserved relative to other scorpion α-toxins. However, a few different amino acids endow it with unique molecular properties, which may be responsible for its specific bioactivities. BmK AGAP-SYPU2, a new scorpion neurotoxin with dual functions, is a potential candidate drug amenable to exploitation and modification.

Resistance of cervical adenocarcinoma cells (HeLa) to venom from the scorpion Centruroides limpidus limpidus

BACKGROUND

The venom of Centruroides limpidus limpidus (Cll) is a mixture of pharmacologically active principles. The most important of these are toxic proteins that interact both selectively and specifically with different cellular targets such as ion channels. Recently, anticancer properties of the venom from other scorpion species have been described. Studies in vitro have shown that scorpion venom induces cell death, inhibits proliferation and triggers the apoptotic pathway in different cancer cell lines. Herein, after treating human cervical adenocarcinoma (HeLa) cells with Cll crude venom, their cytotoxic activity and apoptosis induction were assessed.

RESULTS

Cll crude venom induced cell death in normal macrophages in a dose-dependent manner. However, through viability assays, HeLa cells showed high survival rates after exposure to Cll venom. Also, Cll venom did not induce apoptosis after performing ethidium bromide/acridine orange assays, nor was there any evidence of chromatin condensation or DNA fragmentation.

CONCLUSIONS

Crude Cll venom exposure was not detrimental to HeLa cell cultures. This may be partially attributable to the absence of specific HeLa cell membrane targets for molecules present in the venom of Centruroides limpidus limpidus. Although these results might discourage additional studies exploring the potential of Cll venom to treat human papilloma cervical cancer, further research is required to explore positive effects of crude Cll venom on other cancer cell lines.

Scorpion ethanol extract and valproic acid effects on hippocampal glial fibrillary acidic protein expression in a rat model of chronic-kindling epilepsy induced by lithium chloride-pilocarpine

The present study analyzed the effects of ethanol extracts of scorpion on epilepsy prevention and hippocampal expression of glial fibrillary acidic protein in a lithium chloride-pilocarpine epileptic rat model. Results were subsequently compared with valproic acid. Results showed gradually-increased hippocampal glial fibrillary acidic protein expression following model establishment; glial fibrillary acidic protein mRNA expression was significantly increased at 3 days, reached a peak at 7 days, and then gradually decreased thereafter. Ethanol extracts of scorpion doses of 580 and 1 160 mg/kg, as well as 120 mg/kg valproic acid, led to a decreased number of glial fibrillary acidic protein-positive cells and glial fibrillary acidic protein mRNA expression, as well as decreased seizure grades and frequency of spontaneously recurrent seizures. The effects of 1 160 mg/kg ethanol extracts of scorpion were equal to those of 120 mg/kg valproic acid. These results suggested that the anti-epileptic effect of ethanol extracts of scorpion were associated with decreased hippocampal glial fibrillary acidic protein expression in a rat model of lithium chloride-pilocarpine induced epilepsy.

Scorpion and spider venom peptides: gene cloning and peptide expression

This communication reviews most of the important findings related to venom components isolated from scorpions and spiders, mainly by means of gene cloning and expression. Rather than revising results obtained by classical biochemical studies that report structure and function of venom components, here the emphasis is placed on cloning and identification of genes present in the venomous glands of these arachnids. Aspects related to cDNA library construction, specific or random ESTs cloning, transcriptome analysis, high-throughput screening, heterologous expression and folding are briefly discussed, showing some numbers of species and components already identified, but also shortly mentioning limitations and perspectives of research for the future in this field.

Eukaryotic expression and purification of anti-epilepsy peptide of Buthus martensii Karsch and its protein interactions

The Asian scorpion Buthus martensil Karsch is important in the Chinese traditional medicine where it is used for the treatment of some nervous system diseases. The anti-epilepsy peptide (AEP) is a 61-amino-acid polypeptide extracted from the venom of B. martensil Karsch. Research has confirmed that it has anti-epileptic effects on the rat model of epilepsy. In this experiment, a cDNA library of AEP from the venom of B. martensil Karsch was constructed using RT-PCR; the primer was designed and used for the amplification. An expression vector of AEP was constructed using Pichia pastoris. Vector expression was induced, and protein purification was then performed. Bolting of the interaction molecule of AEP was by His pull down. Experimental results indicate high AEP expression, and the obtained protein was purified and compared with the control group. Four conspicuous protein bands were observed, and mass chromatographic analysis indicated that the four proteins were synaptosomal-associated protein of 25 kDa (SNAP-25), glial fibrillary acidic protein (GFAP), Glutamic acid decarboxylase (GAD) and N-methyl-D: -aspartate (NMDA). Further, the four protein bands were verified by mammalian two-hybrid experiments and co-immunoprecipitation. AEP was found to interact with SNAP2 and NMDA. This provides experimental evidence for the mechanism of AEP's anti-epileptic action and for the manufacture of a novel type anti-epileptic drug.

Indian black scorpion (Heterometrus bengalensis Koch) venom induced antiproliferative and apoptogenic activity against human leukemic cell lines U937 and K562

Venoms are rich source of several bioactive compounds that possess therapeutic potentials. The different constituents of scorpion venom can modulate cell proliferation, cell growth and cell cycle. In the present communication, the cytotoxic activity of Indian black scorpion (Heterometrus bengalensis) venom was explored on human leukemic U937 and K562 cells. Scorpion venom induced U937 and K562 cell growth inhibition and the IC(50) value calculated to be 41.5 microg/ml (U937) and 88.3 microg/ml (K562). The scorpion venom showed characteristic features of apoptosis such as membrane blebbing, chromatin condensation and DNA degradation in both the cells as evidenced by confocal, fluorescence, scanning electron microscopy. Scorpion venom (IC(50) dose, 48 h) induced DNA fragmentation as evidenced by comet formation. Flow-cytometric assay revealed a significant amount of apoptotic cells (early and late) due to scorpion venom treatment. The venom induced cell cycle arrest was observed with maximum cell accumulation at sub-G(1) phase. Thus, the Indian scorpion (H. bengalensis) venom possessed antiproliferative, cytotoxic and apoptogenic activity against human leukemic cells.

Neurotoxins from invertebrates as anticonvulsants: From basic research to therapeutic application

Invertebrate venoms have attracted considerable interest as a potential source of bioactive substances, especially neurotoxins. These molecules have proved to be extremely useful tools for the understanding of synaptic transmission events, and they have contributed to the design of novel drugs for the treatment of neurological disorders and pain. In this context, as epilepsy involves neuronal substrates, which are sites of action of many neurotoxins; venoms may be particularly useful for antiepileptic drug (AED) research. Epilepsy is a chronic disease whose treatment consists of controlling seizures with antiepileptics that very often induce strong undesirable side effects that may limit treatment. Here, we review the vast, but yet unexplored, world of neurotoxins from invertebrates used as probes in pharmacological screening for novel and less toxic antiepileptics. We briefly review (1) the molecular basis of epilepsy, as well as the sites of action of commonly used anticonvulsants (we bring a comprehensive review of the elements from invertebrate venoms which are mostly studied in neuroscience research and may be useful for drug development); (2) peptides from conus snails; (3) peptides and polyamine toxins from spiders and wasps; and (4) peptides from scorpions.

Rat epileptic seizures evoked by BmK αIV and its possible mechanisms involved in sodium channels

This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx. Moreover, BmK alphaIV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK alphaIV-evoked epileptic seizures may be involved in the modulation of BmK alphaIV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca(2+) influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK alphaIV in the central nervous system for understanding epileptogenesis involved in sodium channels.

Development of an improved preparation and an enzyme-linked immunosorbent assay for anti-neuroexcitation peptide (ANEP)

Anti-neuroexcitation peptide (ANEP) is a novel recombinant peptide obtained from the venom of the Chinese scorpion Buthus martensii Karsch. However, the expression of recombinant ANEP in Escherichia coli results in the formation of insoluble aggregates known as inclusion bodies. Here, we describe a novel method for the preparation of ANEP which maximizes the yields of recombinant peptide in a soluble and active form. A non-fusion expression plasmid pNJUTRX-1-ANEP-His(6) encoding recombinant ANEP with a His(6)-tag at its C-terminus was constructed and transformed into E. coli strain BL21 (DE3). The expressed ANEP was almost in soluble form and accounted for about 12% of the total cellular proteins. The recombinant ANEP in the cell lysate was purified to homogeneity by His Bind affinity chromatography. This effective method solved the problem of a lack of sufficient active peptide which, until now, has hampered the further research and development. In order to develop an immunoassay method for ANEP, polyclonal rabbit antiserum was raised against the prepared ANEP and purified by protein A affinity chromatography. It was confirmed that the antibody reacted with recombinant ANEP by both Western blotting and ELISA results. Using purified antibody, the immunoassay method was developed.

Anticonvulsant and Behavioural Effects of the Denatured Venom of the Social Wasp Polybia occidentalis (Polistinae, Vespidae)

Several investigations demonstrate that neurotoxins isolated from venoms of spiders and wasps may exert specific and selective activity on structures of the mammalian CNS. In the present work we examine the neurological effects of the low molecular weight compounds of the denatured venom of the neotropical social wasp Polybia occidentalis in freely moving rats. Central administration of denatured venom decreased the duration of exploratory, elevation and grooming behaviours on the open field. Moreover, denatured venom inhibited convulsing action of bicuculline (ED50 57 microg/microl), picrotoxin (ED50 75 microg/microl) and kainic acid (ED50 44 microg/microl), although it was ineffective against pentylenetetrazole-induced seizures. Despite of its inhibitory activity, toxic effects on motor performance examined in the rotarod test were not found, not even in extremely high doses. Also, denatured venom moderately reduced the spontaneous locomotor activity at anticonvulsant doses. These findings may indicate that the denatured venom has anticonvulsant activity with scarce propensity to cause neurological side-effects. Further studies are necessary to isolate the active compound and establish its mechanism of action.

Anticonvulsant effects of the wasp Polybia ignobilis venom on chemically induced seizures and action on GABA and glutamate receptors

Venoms of spiders and wasps are well recognized to present high affinity to the central nervous tissue of many mammalian species. Here we describe the effects of direct exposure of rat (Rattus norvegicus) brains to the crude and denatured venom of the Brazilian social wasp Polybia ignobilis. Lower doses of crude venom injected via intracerebroventricular (i.c.v.) inhibited the exploratory activity of animals, while higher doses provoked severe generalized tonic-clonic seizures, with hind limb extension. The status epilepticus lasted for few minutes leading the animals to respiratory depression and death. In contrast, the denatured venom was anticonvulsant against acute seizures induced by the i.c.v. injection of bicuculline, picrotoxin and kainic acid, but it was ineffective against seizures caused by systemic pentylenetetrazole. Moreover, the [3H]-glutamate binding in membranes from rat brain cortex was inhibited by the denatured venom in lower concentrations than the [3H]-GABA binding. The denatured venom contains free GABA and glutamate (34 and 802 pg/microg of venom, respectively), but they are not the major binding inhibitors. These interactions of venom components with GABA and glutamate receptors could be responsible for the anticonvulsant effects introducing the venom from P. ignobilis as a potential pharmacological source of anticonvulsant drugs.

A novel short-chain peptide BmKX from the chinese scorpion Buthus martensi karsch, sequencing, gene cloning and structure determination

Scorpion venom is a rich source of bioactive peptides. From the venom of Chinese scorpion Buthus martensi Karsch (BmK), a novel short chain peptide BmKX of 31-amino acid residues was purified, and its amino acid sequence and gene structure were determined. The gene of BmKX was composed of two exons interrupted by an 86-bp intron at the codon-7 upstream of the mature peptide. Although its gene structure is similar to those of other known scorpion toxins, its amino acid sequence, especially the cysteine framework, is different from those of all other known subfamilies of short-chain scorpion toxins. The solution structure of BmKX, determined with two-dimensional NMR spectroscopy, shows that BmKX also forms a typical cysteine-stabilized alpha/beta scaffold adopted by most short-chain scorpion toxins, consisting of a short 3(10)-helix and a two-stranded antiparallel beta-sheet, and the short N-terminal segment forms a pseudo-strand of the beta-sheet. However, the orientation between the helix and the beta-sheet is significantly different from the others, which might be the reason for its unique but still unclear physiological function.

A novel scorpion toxin blocking small conductance Ca2+ activated K+ channel

Small conductance calcium activated potassium channels (SK) are crucial in the regulation of cell firing frequency in the nervous system and other tissues. In the present work, a novel SK channel blocker, designated BmSKTx1, was purified from the scorpion Buthus martensi Karsh venom. The sequence of the N-terminal 22 amino acid residues was determined by Edman degradation. Using this sequence information, the full-length cDNA and genomic gene of BmSKTx1 were cloned and sequenced. By these analyses, BmSKTx1 was found to be a peptide composed of 31 amino acid residues with three disulfide bonds. It shared little sequence homology with other known scorpion alpha-KTxs but showed close relationship with SK channel blockers in the phylogenetic tree. According to the previous nomenclature, BmSKTx1 was classified as alpha-KTx14.1. We examined the effects of BmSKTx1 on different ion channels of rat adrenal chromaffin cells (RACC) and locust dorsal unpaired median (DUM) neurons. BmSKTx1 selectively inhibited apamin-sensitive SK currents in RACC with Kd of 0.72 microM and Hill coefficient of 2.2. And it had no effect on Na+, Ca2+, Kv, and BK currents in DUM neuron, indicating that BmSKTx1 was a selective SK toxin.

Neuroprotection and peptide toxins

Neurodegeneration induced by excitatory neurotransmitter glutamate is considered to be of particular relevance in several types of acute and chronic neurological impairments ranging from cerebral ischaemia to neuropathological conditions such as motor neuron disease, Alzheimer's, Parkinson's disease and epilepsy. The hyperexcitation of glutamate receptors coupled with calcium overload can be prevented or modulated by using well-established competitive and non-competitive antagonists targeting ion/receptor channels. The exponentially increasing body of pharmacological evidence over the years indicates potential applications of peptide toxins, due to their exquisite subtype selectivity on ion channels and receptors, as lead structures for the development of drugs for the treatment of wide variety of neurological disorders. This review comprehensively highlights the overview of the diversity in the molecular as well as neurobiological mechanisms of different peptide toxins derived from venomous animals with particular reference to neuroprotection. In addition, the potential applications of peptide toxins in the diagnosis and treatment of neurological disorders such as neuromuscular disorders, epilepsy, Alzheimer's and Parkinson's diseases, gliomas and ischaemic stroke and their future prospects in the diagnosis as well as in the therapy are addressed.

BmBKTx1, a novel Ca2+-activated K+ channel blocker purified from the Asian scorpion Buthus martensi Karsch

BmBKTx1 is a novel short chain toxin purified from the venom of the Asian scorpion Buthus martensi Karsch. It is composed of 31 residues and is structurally related to SK toxins. However, when tested on the cloned rat SK2 channel, it only partially inhibited rSK2 currents, even at a concentration of 1 microm. To screen for other possible targets, BmBKTx1 was then tested on isolated metathoracic dorsal unpaired median neurons of Locusta migratoria, in which a wide variety of ion channels are expressed. The results suggested that BmBKTx1 could specifically block voltage-gated Ca(2+)-activated K(+) currents (BK-type). This was confirmed by testing the BmBKTx1 effect on the alpha subunits of BK channels of the cockroach (pSlo), fruit fly (dSlo), and human (hSlo), heterologously expressed in HEK293 cells. The IC(50) for channel blocking by BmBKTx1 was 82 nm for pSlo and 194 nm for dSlo. Interestingly, BmBKTx1 hardly affected hSlo currents, even at concentrations as high as 10 microm, suggesting that the toxin might be insect specific. In contrast to most other scorpion BK blockers that also act on the Kv1.3 channel, BmBKTx1 did not affect this channel as well as other Kv channels. These results show that BmBKTx1 is a novel kind of blocker of BK-type Ca(2+)-activated K(+) channels. As the first reported toxin active on the Drosophila Slo channel dSlo, it will also greatly facilitate studying the physiological role of BK channels in this model organism.

Expression of an antitumor-analgesic peptide from the venom of Chinese scorpion Buthus martensii karsch in Escherichia coli

The gene encoding a putative mature antitumor-analgesic peptide (AGAP) from the venom of the Chinese scorpion Buthus martensii Karsch was obtained by polymerase chain reaction (PCR) according to its cDNA sequence and expressed in Escherichia coli. While most of the recombinant AGAP was expressed in the form of insoluble inclusion body. The recombinant AGAP was purified to homogeneity by metal chelating affinity chromatography. Pharmaceutical tests showed that the recombinant AGAP has both analgesic and antitumor activities on mice.

An overview of toxins and genes from the venom of the Asian scorpion Buthus martensi Karsch

Among the different scorpion species, Buthus martensi Karsch (BmK), a widely distributed scorpion species in Asia, has received a lot of attention. Indeed, over the past decade, more than 70 different peptides, toxins or homologues have been isolated and more peptides are probably still to be revealed. This review is focusing on the many peptides isolated from the venom of this scorpion, their targets, their genes and their structures. The aim is to give both a 'state of the art' view of the research on BmK venom and an illustration of the complexity of this scorpion venom. In the present manuscript, we have listed the different ion channel toxins and homologues isolated from the venom of BmK, either from the literature or from databases. We have described here 51 long-chain peptides related to the Na(+) channel toxins family: 34 related to the alpha-toxin family, four related to the excitatory insect toxin family, 10 related to the depressant insect toxin, one beta-like toxin plus two peptides, BmK AS and AS1, that act on ryanodine receptors. We also listed 18 peptides related to the K(+) channel toxin family: 14 short chain toxins or homologues, two long chain K(+) toxin homologues and two putative K(+) toxin precursors. Additionally, two chlorotoxin like peptides (Bm-12 and 12 b) have been isolated in the venom of BmK. Besides these ion channels toxins, two peptides without disulfide bridges (the bradykinin-potentiating peptide BmK bpp and BmK n1) and three peptides with no known functions have also been discovered in this venom. We have also taken the opportunity of this review to update the classification of scorpion K(+) toxins () which now presents 17 subfamilies instead of the 12 described earlier. The work on the venom of BmK led to the discovery of two new subfamilies, alpha-KT x 14 and alpha-KT x 17.

Molecular cloning and functional expression of a gene encoding an antiarrhythmia peptide derived from the scorpion toxin

From a cDNA library of Chinese scorpion Buthus martensii Karsch, full-length cDNAs of 351 nucleotides encoding precursors (named BmKIM) that contain signal peptides of 21 amino acid residues, a mature toxin of 61 residues with four disulfide bridges, and an extra Gly-Lys-Lys tail, were isolated. The genomic sequence of BmKIM was cloned and sequenced; it consisted of two exons disrupted by an intron of 1622 bp, the largest known in scorpion toxin genomes, inserted in the region encoding the signal peptide. The cDNA was expressed in Escherichia coli. The recombinant BmKIM was toxic to both mammal and insects. This is the first report that a toxin with such high sequence homology with an insect-specific depressant toxin group exhibits toxicity to mammals. Using whole cell patch-clamp recording, it was discovered that the recombinant BmKIM inhibited the sodium current in rat dorsal root ganglion neurons and ventricular myocytes and protected against aconitine- induced cardiac arrhythmia.

Purification, structure-function analysis, and molecular characterization of novel linear peptides from scorpion Opisthacanthus madagascariensis

In the previous report [Biochem. Biophys. Res. Commun. 286 (2001) 820], we described a novel short linear peptide, IsCT, with cytolytic activity isolated from the venom of scorpion Opisthacanthus madagascariensis. From the same scorpion venom, we further purified and characterized three short linear peptides named IsCT2, IsCTf, and IsCT2f that shared high homology with IsCT, while with different C-terminal areas between IsCT/IsCT2 and IsCTf/IsCT2f. Structure-activity relationship was analyzed by performing vivo and vitro assays and circular dichroism spectroscopy. Like IsCT, IsCT2 showed broad activity spectra against microbes (Gram positive and negative bacteria as well as fungi) and relatively weak hemolytic activity against sheep red blood cells. It adopts an amphipathic alpha-helical structure in aqueous TFE and is able to disrupt the artificial membrane. However, the other two peptides IsCTf and IsCT2f showed no activity in antimicrobial or hemolytic assay. Furthermore, IsCTf and IsCT2f cannot form amphipathic alpha-helix while demonstrating random coil structure in aqueous TFE, which might result in their lost cytolytic activity. IsCTf and IsCT2f both exist in the crude venom and are proved to be enzymatic products from IsCT and IsCT2. Whether they have some other biological activity is still unclear. In addition, we got the cDNAs encoding the precursors of IsCT and IsCT2. Besides the signal peptide, they still contain an unusual acidic pro-peptide at the C-terminal that was quite different from other known precursors of scorpion venom peptides. The novel structure and biological activity of these peptides proposed them to be a new class in scorpion venom.