Hemitoxin, the first potassium channel toxin from the venom of the Iranian scorpion Hemiscorpius lepturus

Structure-Function Relationship of a Novel MTX-like Peptide (MTX1) Isolated and Characterized from the Venom of the Scorpion Maurus palmatus

Maurotoxin (MTX) is a 34-residue peptide from Scorpio maurus venom. It is reticulated by four disulfide bridges with a unique arrangement compared to other scorpion toxins that target potassium (K+) channels. Structure-activity relationship studies have not been well performed for this toxin family. The screening of Scorpio maurus venom was performed by different steps of fractionation, followed by the ELISA test, using MTX antibodies, to isolate an MTX-like peptide. In vitro, in vivo and computational studies were performed to study the structure-activity relationship of the new isolated peptide. We isolated a new peptide designated MTX1, structurally related to MTX. It demonstrated toxicity on mice eight times more effectively than MTX. MTX1 blocks the Kv1.2 and Kv1.3 channels, expressed in Xenopus oocytes, with IC50 values of 0.26 and 180 nM, respectively. Moreover, MTX1 competitively interacts with both 125I-apamin (IC50 = 1.7 nM) and 125I-charybdotoxin (IC50 = 5 nM) for binding to rat brain synaptosomes. Despite its high sequence similarity (85%) to MTX, MTX1 exhibits a higher binding affinity towards the Kv1.2 and SKCa channels. Computational analysis highlights the significance of specific residues in the β-sheet region, particularly the R27, in enhancing the binding affinity of MTX1 towards the Kv1.2 and SKCa channels.

Analysis of Some Putative Novel Peptides from Iranian Scorpion Venom Glands, Hemiscorpius lepturus, Using cDNA Library Construction

Background: To date, more than 300,000 distinct peptides have been identified in scorpion venom. However, only a limited number of these peptides have been described. Objectives: We characterized some putative peptides from the venom gland cDNA library of the Iranian yellow scorpion Hemiscorpius lepturus”. Methods: Total RNA was extracted from yellow Iranian scorpion glands. Single-stranded cDNA (sscDNA) and double-stranded cDNA (dscDNA) were synthesized by polymerase chain reaction (PCR). A cDNA library was achieved by inserting dscDNA into a special vector and subsequently transformed to chemically competent Escherichia coli as a host. The library was screened by culturing the liquid library on Lysogeny broth (LB)-agar plates. Analysis of positive clones was performed by plasmid extraction and the sequencing of the inserts. Finally, all cDNA sequences were analyzed and characterized by bioinformatics software. Results: One hundred colonies were randomly analyzed. Eighty-nine cDNA sequences had acceptable quality for bioinformatics analysis. Five sequences were selected for further analysis. The peptides related to these sequences were divided into two groups, non-disulfide bridge peptides (NDBP) and disulfide bridge peptides (DBP), the application of which in health and medical issues has been suggested. Conclusions: The data obtained in this study may be an important resource for further in vivo and in vitro functional assays to identify valuable therapeutic peptides.

Discovery of Leptulipin, a New Anticancer Protein from theIranian Scorpion, Hemiscorpius lepturus

Cancer is one of the leading causes of mortality in the world. Unfortunately, the present anticancer chemotherapeutics display high cytotoxicity. Accordingly, the discovery of new anticancer agents with lower side effects is highly necessitated. This study aimed to discover an anticancer compound from Hemiscorpius lepturus scorpion venom. Bioactivity-guided chromatography was performed to isolate an active compound against colon and breast cancer cell lines. 2D electrophoresis and MALDI-TOF were performed to identify the molecule. A partial protein sequence was obtained by mass spectrometry, while the full-length was deciphered using a cDNA library of the venom gland by bioinformatics analyses and was designated as leptulipin. The gene was cloned in pET-26b, expressed, and purified. The anticancer effect and mechanism action of leptulipin were evaluated by MTT, apoptosis, and cell cycle assays, as well as by gene expression analysis of apoptosis-related genes. The treated cells displayed inhibition of cell proliferation, altered morphology, DNA fragmentation, and cell cycle arrest. Furthermore, the treated cells showed a decrease in BCL-2 expression and an increase in Bax and Caspase 9 genes. In this study, we discovered a new anticancer protein from H. lepturus scorpion venom. Leptulipin showed significant anticancer activity against breast and colon cancer cell lines.

Sajedi R, Pooshang Bagheri K, Sabatier JM, Shahbazzadeh D. Novel Mutant Phospholipase D from Hemiscorpius lepturus Acts as A Highly Immunogen in BALB/c Mice Against the Lethality of Scorpion Venom

Hemiscorpius lepturus (H. lepturus) which belongs to the Scorpionidae family, is the deadliest scorpion in Iran. It causes pathological manifestations like dermonecrosis, hemolysis, renal failure, necrotic ulcers, and in some cases, even death. The venom of this scorpion is well-known for its cytotoxic effects in comparison with the other venomous scorpions which show significant neurotoxic effects. Due to the painless nature of the sting of this scorpion, the clinical symptoms occur in victims 24 to 72 h post-sting. In our previous studies during the last decade, we demonstrated that the medical complications are attributable to the presence of phospholipase D (PLD) as a major toxin in the venom. With the purpose of designing and constructing a vaccine against H. lepturus for humans, animal model experiments were performed. To achieve this goal, non-toxic PLD was developed by mutation of two critical catalytic residues-His12 and His48-into alanines and the product was then denominated mut-rPLD1. The in-vivo tests showed that the mice immunized with interval doses of 10 µg of mut-rPLD1, were completely protected against 10× the LD100 of the venom. In conclusion, this mutant may be an effective vaccine candidate against scorpion envenomation by H. lepturus in future clinical studies.

Venoms of Iranian Scorpions (Arachnida, Scorpiones) and Their Potential for Drug Discovery

Scorpions, a characteristic group of arthropods, are among the earliest diverging arachnids, dating back almost 440 million years. One of the many interesting aspects of scorpions is that they have venom arsenals for capturing prey and defending against predators, which may play a critical role in their evolutionary success. Unfortunately, however, scorpion envenomation represents a serious health problem in several countries, including Iran. Iran is acknowledged as an area with a high richness of scorpion species and families. The diversity of the scorpion fauna in Iran is the subject of this review, in which we report a total of 78 species and subspecies in 19 genera and four families. We also list some of the toxins or genes studied from five species, including Androctonus crassicauda, Hottentotta zagrosensis, Mesobuthus phillipsi, Odontobuthus doriae, and Hemiscorpius lepturus, in the Buthidae and Hemiscorpiidae families. Lastly, we review the diverse functions of typical toxins from the Iranian scorpion species, including their medical applications.

Scorpion toxins targeting Kv1.3 channels: insights into immunosuppression

Scorpion venoms are natural sources of molecules that have, in addition to their toxic function, potential therapeutic applications. In this source the neurotoxins can be found especially those that act on potassium channels. Potassium channels are responsible for maintaining the membrane potential in the excitable cells, especially the voltage-dependent potassium channels (Kv), including Kv1.3 channels. These channels (Kv1.3) are expressed by various types of tissues and cells, being part of several physiological processes. However, the major studies of Kv1.3 are performed on T cells due its importance on autoimmune diseases. Scorpion toxins capable of acting on potassium channels (KTx), mainly on Kv1.3 channels, have gained a prominent role for their possible ability to control inflammatory autoimmune diseases. Some of these toxins have already left bench trials and are being evaluated in clinical trials, presenting great therapeutic potential. Thus, scorpion toxins are important natural molecules that should not be overlooked in the treatment of autoimmune and other diseases.

Venom-Derived Peptide Modulators of Cation-Selective Channels: Friend, Foe or Frenemy

Ion channels play a key role in our body to regulate homeostasis and conduct electrical signals. With the help of advances in structural biology, as well as the discovery of numerous channel modulators derived from animal toxins, we are moving toward a better understanding of the function and mode of action of ion channels. Their ubiquitous tissue distribution and the physiological relevancies of their opening and closing suggest that cation channels are particularly attractive drug targets, and years of research has revealed a variety of natural toxins that bind to these channels and alter their function. In this review, we provide an introductory overview of the major cation ion channels: potassium channels, sodium channels and calcium channels, describe their venom-derived peptide modulators, and how these peptides provide great research and therapeutic value to both basic and translational medical research.

Developing recombinant phospholipase D1 (rPLD1) toxoid from Iranian Hemiscorpius lepturus scorpion and its protective effects in BALB/c mice

Hemiscorpius lepturus (H. lepturus) is one of the most dangerous scorpions and the most medically important scorpion in Iran. The clinical signs of H. lepturus envenomation, including dermonecrosis, hematuria, renal failure and early death, are attributed to phospholipase D activity. This study was conducted to develop a novel recombinant phospholipase D1 (rPLD1) toxoid and investigate its immunogenicity and protective effects against the lethality of H. lepturus venom. The lethal protein recombinant phospholipase D1 was expressed from PLD H. lepturus venom gland. The rPLD1 toxin was converted into toxoid (the first toxoid of H. lepturus PLD) with a 0.25% concentration of formalin and stored for ten days at room temperature. In the toxicity test, the lethal activity of recombinant phospholipase D1 was fully inhibited. When it reached up to 3 times higher than the maximal effective concentration of the purified toxin (11.1 μg), rPLD1 toxoid was used. The sphingomyelinase activity was inhibited when up to 5.4 times of the LD100 of the purified toxin (20 μg), toxoid was used. It was then used to produce an antibody in BALB/c as an antigen and the mice were then challenged with rPLD1 toxin and the whole venom. The immunogenicity of rPLD1 toxoid was evaluated and the maximum titer of the raised antibodies was determined by ELISA assay. The optimum titer for anti-rPLD1 toxoid sera was obtained at the third intraperitoneal injection of rPLD1 toxoid, and a high titer was reached at the fourth injection in the mice. This toxoid increased the amount of antibodies and produced a protective antiserum against the whole venom of H. lepturus and rPLD1 toxin. The in-vivo test results showed that the mice were completely resistant against 200 times the LD100 of recombinant phospholipase D1 and the whole venom of H. lepturus. To conclude, rPLD1 can be used in toxoid form as an immunogen in the production of a new generation of neutralizing antibodies against the lethality and toxicity of H. lepturus whole venom.

Scorpionism by Hemiscorpius spp. in Iran: a review

Scorpions are distributed throughout Iran and the genus Hemiscorpius is particularly important in this region. Hemiscorpius lepturus is the most significant species within the genus in the country. Since scorpionism provoked by Hemiscorpius comprises a medical emergency, the present study is focused on this important issue. In order to perform the present work, a review of the medical and health-related literature was carried out in several databases. The current findings indicate that six species of Hemiscorpius are found in 15 states of Iran, mainly in the south and southwest. Deaths caused by stings were reported only for two species. The morphological characteristics and geographical distribution of H. lepturus in Iran, its venom and the toxic compounds, epidemiologic data and clinical manifestations of envenomation as well as treatment for affected people are herein reviewed and described. H. lepturus venom toxicity differs from other Iranian scorpions regarding duration and severity. Scorpionism is an important public health problem in Iran, especially in southwest and south regions and in urban areas. It is more prevalent in children and young people. H. lepturus venom is primarily a cytotoxic agent and has hemolytic, nephrotoxic and to some extent hepatotoxic activity. The use of polyvalent antivenom to prevent scorpion sting symptoms is recommended. A well-planned health education program might be useful in preventing scorpionism.

Arthropod toxins acting on neuronal potassium channels

Arthropod venoms are a rich mixture of biologically active compounds exerting different physiological actions across diverse phyla and affecting multiple organ systems including the central nervous system. Venom compounds can inhibit or activate ion channels, receptors and transporters with high specificity and affinity providing essential insights into ion channel function. In this review, we focus on arthropod toxins (scorpions, spiders, bees and centipedes) acting on neuronal potassium channels. A brief description of the K⁺ channels classification and structure is included and a compendium of neuronal K⁺ channels and the arthropod toxins that modify them have been listed. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

The inhibitory activity of HL-7 and HL-10 peptide from scorpion venom (Hemiscorpius lepturus) on angiotensin converting enzyme: Kinetic and docking study

The hypertension is one of the highest risk factors for stroke, myocardial infarction, vascular disease and chronic kidney disease. Angiotensin converting enzyme (ACE) has an important role in the physiological regulation of cardiovascular system. ACE inhibition is a key purpose for hypertension treatment. In this study, two peptides named HL-7 with the sequence of YLYELAR (MW: 927.07Da) and HL-10 with the sequence of AFPYYGHHLG (MW: 1161.28Da) were identified from scorpion venom of H. lepturus. The inhibitory activity of HL-7 and HL-10 was examined on rabbit ACE. The inhibition mechanisms were assayed by kinetic and docking studies. The IC₅₀ values for ACE inhibition of HL-7 and HL-10 were 9.37µM and 17.22µM, respectively. Lineweaver-Burk plots showed that two peptides inhibited rabbit ACE with competitive manner. The molecular docking conformed experimental results and showed that the two peptides interacted with N-domain and C-domain active sites. Also, docking study revealed that the two peptides can form hydrogen and hydrophobic bonds at their binding sites. Both peptides had higher affinity to N-domain. Our results showed that HL-7 exhibited more strong interactions with amino acids at active site. It seems that HL-10 peptide could occupy more space, thereby inhibiting the substrate entrance to active site.

Characteristics and Lethality of a Novel Recombinant Dermonecrotic Venom Phospholipase D from Hemiscorpius lepturus

Hemoscorpius lepturus is the most medically important scorpion in Iran. The clinical signs of H. lepturus envenomation are remarkably similar to those reported for brown spiders, including dermonecrosis, hematuria, renal failure and even death. The lethality and toxicity of brown spiders’ venom have been attributed to its phospholipase D activity. This study aims to identify a phospholipase D with possible lethality and dermonecrotic activity in H. lepturus venom. In this study, a cDNA library of the venom glands was generated by Illumina RNA sequencing. Phospholipase D (PLD) from H. lepturus was characterized according to its significant similarity with PLDs from brown spiders. The main chain designated as Hl-RecPLD1 (the first recombinant isoform of H. lepturus PLD) was cloned, expressed and purified. Sphingomyelinase, dermonecrotic and lethal activities were examined. Hl-PLD1 showed remarkable sequence similarity and structural homology with PLDs of brown spiders. The conformation of Hl-PLD1 was predicted as a “TIM beta/alpha-barrel”. The lethal dose 50 (LD₅₀) and dermonecrotic activities of Hl-RecPLD1 were determined as 3.1 µg/mouse and 0.7 cm² at 1 µg respectively. It is the first report indicating that a similar molecular evolutionary mechanism has occurred in both American brown spiders and this Iranian scorpion. In conclusion, Hl-RecPLD1 is a highly active phospholipase D, which would be considered as the lethal dermonecrotic toxin in H. lepturus venom.

Identification of the immunogenic epitopes of the whole venom component of the Hemiscorpius lepturus scorpion using the phage display peptide library

The venom of the Hemiscorpius lepturus scorpion contains mixtures of bioactive compounds that disturb biochemical and physiological functions of the victims. Hemiscorpius lepturus envenomation is recognized as a serious health concern in tropical regions. So far, there is no preventive procedure, and the main focus is on treatment of victims with an antiserum purified from hyper-immunized horses. Although antisera can neutralize the venom, they, in some cases, lead to anaphylactic shock and even death. Selection of peptides mimicking antigenic and immunogenic epitopes of toxins from random peptide libraries is a novel approach for the development of recombinant toxins and poly-epitopic vaccine. To achieve this aim, a phage display peptide library and three rounds of biopanning were performed on immobilized antibodies (IgGs) purified from the sera of hyper-immunized horses. The results show that the highest binding of the phage to immobilized horse antibodies occurred in the third round of biopanning. Over 125 individual clones carrying mimotopes of Hemiscorpius lepturus toxins were selected and subjected for sequencing. The sequencing results identified unique peptides mimicking the antigenic and immunogenic epitopes of Hemiscorpius lepturus toxins. The results of this study provide a basis for further studies and the development of a putative epitopic vaccine and a recombinant toxin.

Scorpion toxin peptide action at the ion channel subunit level

This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

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.

Active Sites of Spinoxin, a Potassium Channel Scorpion Toxin, Elucidated by Systematic Alanine Scanning

Peptide toxins from scorpion venoms constitute the largest group of toxins that target the voltage-gated potassium channel (Kv). Spinoxin (SPX) isolated from the venom of scorpion Heterometrus spinifer is a 34-residue peptide neurotoxin cross-linked by four disulfide bridges. SPX is a potent inhibitor of Kv1.3 potassium channels (IC50 = 63 nM), which are considered to be valid molecular targets in the diagnostics and therapy of various autoimmune disorders and cancers. Here we synthesized 25 analogues of SPX and analyzed the role of each amino acid in SPX using alanine scanning to study its structure-function relationships. All synthetic analogues showed similar disulfide bond pairings and secondary structures as native SPX. Alanine replacements at Lys(23), Asn(26), and Lys(30) resulted in loss of activity against Kv1.3 potassium channels, whereas replacements at Arg(7), Met(14), Lys(27), and Tyr(32) also largely reduced inhibitory activity. These results suggest that the side chains of these amino acids in SPX play an important role in its interaction with Kv1.3 channels. In particular, Lys(23) appears to be a key residue that underpins Kv1.3 channel inhibition. Of these seven amino acid residues, four are basic amino acids, suggesting that the positive electrostatic potential on the surface of SPX is likely required for high affinity interaction with Kv1.3 channels. This study provides insight into the structure-function relationships of SPX with implications for the rational design of new lead compounds targeting potassium channels with high potency.

First report of death due to Hemiscorpius acanthocercus envenomation in Iran: Case report

Scorpion stings are significant causes of death in the western and southern regions of Iran. To date, reports have indicated that the H. lepturus species is the main cause of mortality due to scorpion stings. One of the species that belongs to this genus is Hemiscorpius acanthocercus (H. acanthocercus). This scorpion's venom is cytotoxic, and it causes pathological changes in the blood and can cause severe damage to the kidneys. The pain of Hemiscorpius' sting is mild and asymptomatic in the early hours. Delays in the treatment of these victims can cause hemolysis, hematuria, kidney failure, and even death. In this paper, we report the first known death due to an H. acanthocercus' sting in Iran.

Scorpion sting nephropathy

Scorpion envenomations are ubiquitous, but nephropathy is a rare manifestation, reported mainly from the Middle East and North Africa. Rapid venom redistribution from blood, delayed excretion from the kidneys, direct toxicity of venom enzymes, cytokine release and afferent arteriolar constriction have been seen in experimental animals. Haemoglobinuria, acute tubular necrosis, interstitial nephritis and haemolytic–uraemic syndrome have been documented in human victims of scorpion envenomation. Epidemiology, venom components and toxins, effects on the laboratory mammals especially the kidneys and reports of renal failure in humans are reviewed in this article.

NMR-based metabonomics survey in rats envenomed by Hemiscorpius lepturus venom

About 1% of scorpion stings in Iran have been reported in cities and more than 5% in rural areas. The genus Hemiscorpous lepturus belongs to the family Hemiscorpiidae that is endemic in the south-western province of Khoozestan and other parts of western Iran. Although this species is responsible for only 10% of the reported stings, it is also responsible for 95% of mortalities. The heavy cytotoxic and neurotoxic venomous effects of scorpion sting may cause serious disorders such as erythema, purpuric changes, bulla, necrosis and ulcer, either alone or in combination. The toxic effects of H. lepturus venom cause vast changes in both primary and secondary metabolites of the victim, which finally lead to death if not treated early enough. Metabolomics is the systematic study of chemical fingerprints resulting from cytotoxic and pathogenic reactions of cells. We studied the toxic mechanism of H. lepturus venom on metabolome profiling of the victims along with biochemical pathways, organs and physiological detectable effects of this venom by the help of (1)H NMR. Our results showed that pyrimidine, histidine and tyrosine metabolisms, and steroid hormone biosynthesis were the most affected pathways. The major action of the crude venom is on the pancreas, and also on the nerve cells, spleen and mitochondria, causing acute seizures, which resemble the early markers of myocardial injury and seizure disorders.

A camelid antibody candidate for development of a therapeutic agent against Hemiscorpius lepturus envenomation

Hemiscorpius lepturus scorpionism poses one of the most dangerous health problems in many parts of the world. The common therapy consists of using antivenom antibody fragments derived from a polyclonal immune response raised in horses. However, this immunotherapy creates serious side effects, including anaphylactic shock sometimes even leading to death. Thus, many efforts have been made to introduce new replacement therapeutics that cause less adverse reactions. One of the most attractive approaches to replacing the available therapy is offered by single-domain antibody fragments, or nanobodies (Nbs). We immunized dromedaries with H. lepturus toxin and identified a functional recombinant Nb (referred to as F7Nb) against heminecrolysin (HNc), the major known hemolytic and dermonecrotic fraction of H. lepturus venom. This Nb was retrieved from the immune library by phage display selection. The in vitro neutralization tests indicated that 17.5 nmol of the F7Nb can inhibit 45% of the hemolytic activity of 1 EC100 (7.5 μg/ml) of HNc. The in vivo neutralization tests demonstrated that F7Nb had good antihemolytic and antidermonecrotic effects against HNc in all tested mice. Surprisingly, F7Nb (8.75 nmol) neutralized 1 LD100 of HNc (10 μg) via an intracerebroventricular route or 1 LD100 (80 μg) via a subcutaneous route. All of the control mice died. Hence, this Nb is a potential leading novel candidate for treating H. lepturus scorpionism in the near future.

The antibody targeting the E314 peptide of human Kv1.3 pore region serves as a novel, potent and specific channel blocker

Selective blockade of Kv1.3 channels in effector memory T (T(EM)) cells was validated to ameliorate autoimmune or autoimmune-associated diseases. We generated the antibody directed against one peptide of human Kv1.3 (hKv1.3) extracellular loop as a novel and possible Kv1.3 blocker. One peptide of hKv1.3 extracellular loop E3 containing 14 amino acids (E314) was chosen as an antigenic determinant to generate the E314 antibody. The E314 antibody specifically recognized 63.8KD protein stably expressed in hKv1.3-HEK 293 cell lines, whereas it did not recognize or cross-react to human Kv1.1(hKv1.1), Kv1.2(hKv1.2), Kv1.4(hKv1.4), Kv1.5(hKv1.5), KCa3.1(hKCa3.1), HERG, hKCNQ1/hKCNE1, Nav1.5 and Cav1.2 proteins stably expressed in HEK 293 cell lines or in human atrial or ventricular myocytes by Western blotting analysis and immunostaining detection. By the technique of whole-cell patch clamp, the E314 antibody was shown to have a directly inhibitory effect on hKv1.3 currents expressed in HEK 293 or Jurkat T cells and the inhibition showed a concentration-dependence. However, it exerted no significant difference on hKv1.1, hKv1.2, hKv1.4, hKv1.5, hKCa3.1, HERG, hKCNQ1/hKCNE1, L-type Ca(2+) or voltage-gated Na(+) currents. The present study demonstrates that the antibody targeting the E314 peptide of hKv1.3 pore region could be a novel, potent and specific hKv1.3 blocker without affecting a variety of closely related K(v)1 channels, KCa3.1 channels and functional cardiac ion channels underlying central nervous system (CNS) disorders or drug-acquired arrhythmias, which is required as a safe clinic-promising channel blocker.

Brachial plexopathy as a rare presenting manifestation of scorpion envenomation

We report a patient who experienced a rare manifestation of an acute, severe brachial plexopathy as the initial complication of scorpion (presumed Hemiscorpius lepturus species) envenomation. Features suggesting conduction block, due to either proximal demyelination or ion channel dysfunction, along with axonal loss were seen on serial electrophysiological studies. Possible mechanisms of the brachial plexopathy include direct compression from tissue edema or a toxic effect on the membrane channels along the nerve.