An overview of some enzymes from buthid scorpion venoms from Colombia: Centruroides margaritatus, Tityus pachyurus, and Tityus n. sp. aff. metuendus

Background

In Colombia, several species of Buthidae scorpions belonging to the genera Centruroides and Tityus coexist, and their stings are considered life-threatening to humans because of their venom neurotoxins. Despite previous studies focusing on neurotoxins from these scorpion genera, little is known about the enzymes present in their venoms and their relationship with whole venom toxicity.

Methods

Here, using proteomic and biochemical protocols the enzymatic activities of the venoms of three Colombian scorpion species, C. margaritatus, T. pachyurus, and T. n. sp. aff. metuendus, were compared to establish the presence and absence of enzymes such as phospholipases, hyaluronidases, and proteases that could be related to venom toxicity. Results: C. margaritatus was positive for hyaluronidases, T. n. sp. aff. metuendus for proteases, and T. pachyurus exhibited activity for all three mentioned enzymes.

Conclusion

This information provides valuable insights into the specific enzyme diversity of each species' venom and their potential role in venom toxicity, which could contribute to the development of better treatments and prevention strategies for scorpion envenomation.

Recombinant expression and antigenicity of two peptide families of neurotoxins from Androctonus sp

Background

Scorpion neurotoxins such as those that modify the mammalian voltage-gated sodium ion channels (Nav) are the main responsible for scorpion envenomation. Their neutralization is crucial in the production of antivenoms against scorpion stings.

Methods

In the present study, two in silico designed genes - one that codes for a native neurotoxin from the venom of the Anatolian scorpion Androctonus crassicauda, named Acra 4 - and another non-native toxin - named consensus scorpion toxin (SccTx) obtained from the alignment of the primary structures of the most toxic neurotoxins from the Middle Eastern and North African scorpions - were recombinantly expressed in E. coli Origami.

Results

Following bacterial expression, the two expressed neurotoxins, hereafter named HisrAcra4 and HisrSccTx, were obtained from inclusion bodies. Both recombinant neurotoxins were obtained in multiple Cys-Cys isoforms. After refolding, the active protein fractions were identified with molecular masses of 8,947.6 and 9,989.1 Da for HisrAcra4 and HisrSccTx, respectively, which agreed with their expected theoretical masses. HisrAcra4 and HisrSccTx were used as antigens to immunize two groups of rabbits, to produce either anti-HisrAcra4 or anti-HisrSccTx serum antibodies, which in turn could recognize and neutralize neurotoxins from venoms of scorpion species from the Middle East and North Africa. The antibodies obtained from rabbits neutralized the 3LD₅₀ of Androctonus australis, Leiurus quinquestriatus hebraeus and Buthus occitanus venoms, but they did not neutralize A. crassicauda and A. mauritanicus venoms. In addition, the anti-HisrAcra4 antibodies did not neutralize any of the five scorpion venoms tested. However, an antibody blend of anti-HisrAcra4 and anti-HisrSccTx was able to neutralize A. crassicauda and A. mauritanicus venoms.

Conclusions

Two recombinant Nav neurotoxins, from different peptide families, were used as antigens to generate IgGs for neutralizing scorpion venoms of species from the Middle East and North Africa.

Effect of recreational exercise and fitness on left ventricular torsion and wall mechanics study (FIT-TWIST/Health)

Background

Left ventricular (LV) remodeling is associated with elite athletics. This study aimed to assess the effects of recreational exercise on LV remodeling and mechanics in healthy adults.

Methods

A prospective cross-sectional study evaluated 38 healthy adult recreational exercise participants with a Bruce protocol treadmill exercise stress test, and 2D and speckle-tracking echocardiography. Fitness level was stratified by the achieved age- and sex-predicted metabolic equivalents (METS) as average/good (group A, N=20; METS=13.9) and high (group B, N=18; METS=18.2) groups.

Results

Mean age was 33 years, and 58% were female. Participants in Group B used more multi-modality (67 vs 20%; p=0.008) or running (50% vs 15%; p=0.04) exercise regimens, and had larger LV mass (66 vs 56 g/m2; p=0.05) and left atrial volume indices (28 vs 22 ml/m2; p=0.02), when compared with group A. However, all LV strain and torsion mechanics were similar between groups (Figure). Multivariate linear regression analysis revealed independent associations between global longitudinal strain (GLS) and transmitral E-wave (β=−0.57), maximum systolic blood pressure (β=0.32), and LV end-diastolic volume index (β=0.32) (model r=0.72; p<0.001). No correlation between METS achieved and LV parameters was observed.

Conclusion

Recreational exercise and fitness are associated with healthy LV geometry and mechanics in adults. Early diastolic LV filling, LV chamber size, and peak exercise blood pressure are correlated with GLS.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Florida Heart Research Foundation

Anticoagulation and bleeding events in Patients with Post- Operative Atrial Fibrillation After Cardiac Surgery

Background

Post-operative atrial fibrillation (POPAF) following cardiac surgery is a common arrhythmia associated with an increased morbidity and mortality. There is little data evaluating the safety and effectiveness of anticoagulation (AC) in POPAF patients. We investigated the occurrence of 30-days POP major bleeding or embolic events and their timing in relation to the index cardiac surgery, the initiation of the arrhythmia and of anticoagulation in patients who developed new onset POPAF.

Methods

4,073 consecutive patients undergoing cardiac surgery from September 2010- December 2016 were evaluated. Patients with history of AF/Aflutter were excluded. POPAF was confirmed by ECG or telemetry. Major post-operative bleeding that occurred after AF was defined using PLATO criteria or the BARC scale (any ≥3).

Results

3,230 patients were included (37% CABG, 69% valve surgery). The incidence of POAF was 24%. The median time (IQR) of POPAF was 3 (2) days after the index surgery. 64% of POAF patients were male and 14% had a history of stroke. The mean (SD) age was 72 (9) years old. The average (SD) CHA2DS2-VASc score was 3.9 (1.5). The initial postoperative AC was full dose heparin, lovenox or argatroban in 58% of patients. The rest of patients had low dose heparin/lovenox for DVT prophylaxis and/or were started on oral anticoagulation without a bridge. The median (IR) time of POPAF to anticoagulation was 1 (2) days. There were 15 (1.9%) major bleeding events; 88% of which occurred in patients receiving full anticoagulation. Major bleeding events occurred a median of 15 (9) days after the index surgery and 9 (6) days after anticoagulation. Independent predictors of major bleed were history of PAD (P<0.01) and pre-operative use of b-blockers (P=0.04). There were 11 (1.4%) POP strokes which occurred a median of 5 (16) days after the index surgery, and 2 (13) days after POPAF. 63% of strokes happened in patients that received anticoagulation. The mean CHA2DS2-VASc score were 3.9 (1.5) and 4.7 (1.7), P=0.1 for patients without and with strokes, respectively. Stroke history (P<0.01) was the only independent stroke predictor. Both strokes and bleeding events were associated with significantly longer ICU and hospital length of stay. 86% of POPAF patients received amiodarone during hospitalization and 2.1% electric cardioversion. Upon discharge, 2.3% of patients were in in atrial fibrillation and 0.8% in atrial flutter.

Conclusion

The post-operative course of major bleeds and stroke in patients with POPAF after cardiac surgery is different. Bleeding events are delayed and appear related to anticoagulation. The relative benefit of perioperative anticoagulation remains unclear.

Funding Acknowledgement

Type of funding sources: None.

Identification of a crocodylian β-defensin variant from Alligator mississippiensis with antimicrobial and antibiofilm activity

β-defensin host defense peptides are important components of the innate immune system of vertebrates. Although evidence of their broad antimicrobial, antibiofilm and immunomodulatory activities in mammals have been presented, β-defensins from other vertebrate species, like crocodylians, remain largely unexplored. In this study, five new crocodylian β-defensin variants from Alligator mississippiensis and Crocodylus porosus were selected for synthesis and characterization based on their charge and hydrophobicity values. Linear peptides were synthesized, folded, purified and then evaluated for their antimicrobial and antibiofilm activities against the bacterial pathogens, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Enterobacter cloacae and Acinetobacter baumannii. The Am23SK variant (SCRFSGGYCIWNWERCRSGHFLVALCPFRKRCCK) from A. mississippiensis displayed promising activity against both planktonic cells and bacterial biofilms, outperforming the human β-defensin 3 under the experimental conditions. Moreover, Am23SK exhibited no cytotoxicity towards mammalian cells and exerted immunomodulatory effects in vitro, moderately suppressing the production of proinflammatory mediators from stimulated human bronchial epithelial cells. Overall, our results have expanded the activity landscape of crocodylian and reptilian β-defensin in general.

A Novel Insecticidal Spider Peptide that Affects the Mammalian Voltage-Gated Ion Channel hKv1.5

Spider venoms include various peptide toxins that modify the ion currents, mainly of excitable insect cells. Consequently, scientific research on spider venoms has revealed a broad range of peptide toxins with different pharmacological properties, even for mammal species. In this work, thirty animal venoms were screened against hKv1.5, a potential target for atrial fibrillation therapy. The whole venom of the spider Oculicosa supermirabilis, which is also insecticidal to house crickets, caused voltage-gated potassium ion channel modulation in hKv1.5. Therefore, a peptide from the spider O. supermirabilis venom, named Osu1, was identified through HPLC reverse-phase fractionation. Osu1 displayed similar biological properties as the whole venom; so, the primary sequence of Osu1 was elucidated by both of N-terminal degradation and endoproteolytic cleavage. Based on its primary structure, a gene that codifies for Osu1 was constructed de novo from protein to DNA by reverse translation. A recombinant Osu1 was expressed using a pQE30 vector inside the E. coli SHuffle expression system. recombinant Osu1 had voltage-gated potassium ion channel modulation of human hKv1.5, and it was also as insecticidal as the native toxin. Due to its novel primary structure, and hypothesized disulfide pairing motif, Osu1 may represent a new family of spider toxins.

AMPK mediates regulation of voltage-gated calcium channels by leptin in isolated neurons from arcuate nucleus

Neuronal control of the energy homeostasis requires the arcuate nucleus of the hypothalamus. This structure integrates peripheral and central signals concerning the energy state of the body. It comprises two populations of neurons releasing anorexigenic and orexigenic peptides, among others. Both populations are regulated by leptin, an anorexigenic hormone, released by white adipose tissue. Voltage-gated calcium entry is critical to promote neurotransmitter and hormone release. It is already known that calcium channel current is inhibited by leptin in orexigenic neurons. However, fine-tuning details of calcium channel regulation in arcuate nucleus by leptin remain to be elucidated. This work aimed to investigate whether 5' adenosine monophosphate-activated protein kinase (AMPK) underlies the leptin-induced inhibition of calcium channels. By using patch-clamping methods, immunocytochemical, and biochemical reagents, we recorded calcium channel currents in orexigenic neuropeptide Y neurons of the arcuate nucleus of rats. Consistently, leptin inhibition of the calcium channel current was not only prevented by AMPK inhibition with Compound C but also hampered with 5-aminoimidazole-4-carboxamide ribonucleoside. Furthermore, leptin selectively inhibited L-type calcium channel current amplitude without major changes in voltage dependence or current kinetics. These results support for the first time the key role of AMPK in the maintenance and regulation of voltage-gated calcium channels. Together, they advance our understanding of the regulation of calcium channels in the central nervous system and emerging questions concerning food intake and energy balance.NEW & NOTEWORTHY Our results readily support the hypothesis that AMPK is responsible for the maintenance of the calcium current and mediates the fine-tuning modulation of the leptin response. The novelty of these results strengthens the critical role of AMPK in the general energy balance and homeostasis.

Key amino acid residues involved in mammalian and insecticidal activities of Magi4 and Hv1b, cysteine-rich spider peptides from the δ-atracotoxin family

δ-Atracotoxins, also known as δ-hexatoxins, are spider neurotoxic peptides, lethal to both vertebrates and insects. Their mechanism of action involves the binding to of the S3/S4 loop of the domain IV of the voltage-gated sodium channels (Na_v). Because of the chemical difficulties of synthesizing folded synthetic δ-atracotoxins correctly, here we explore an expression system that is designed to produce biologically active recombinant δ-atracotoxins, and a number of variants, in order to establish certain amino acids implicated in the pharmacophore of this lethal neurotoxin. In order to elucidate and verify which amino acid residues play a key role that is toxic to vertebrates and insects, amino acid substitutes were produced by aligning the primary structures of several lethal δ-atracotoxins with those of δ-atracotoxins-Hv1b; a member of the δ-atracotoxin family that has low impact on vertebrates and is not toxic to insects. Our findings corroborate that the substitutions of the amino acid residue Y22 from δ-atracotoxin-Mg1a (Magi4) to K22 in δ-atracotoxin-Hv1b reduces its mammalian activity. Moreover, the substitutions of the amino acid residues Y22 and N26 from δ-atracotoxin-Mg1a (Magi4) to K22 and N26 in δ-atracotoxin-Hv1b reduces its insecticidal activity. Also, the basic residues K4 and R5 are important for keeping such insecticidal activity. Structural models suggest that such residues are clustered onto two bioactive surfaces, which share similar areas, previously reported as bioactive surfaces for scorpion α-toxins. Furthermore, these bioactive surfaces were also found to be similar to those found in related spider and anemone toxins, which affect the same Na_v receptor, indicating that these motifs are important not only for scorpion but may be also for animal toxins that affect the S3/S4 loop of the domain IV of the Na_v.

Role of alkaline phosphatase from Manduca sexta in the mechanism of action of Bacillus thuringiensis Cry1Ab toxin

Cry toxins produced by Bacillus thuringiensis have been recognized as pore-forming toxins whose primary action is to lyse midgut epithelial cells in their target insect. In the case of the Cry1A toxins, a prepore oligomeric intermediate is formed after interaction with cadherin receptor. The Cry1A oligomer then interacts with glycosylphosphatidylinositol-anchored receptors. Two Manduca sexta glycosylphosphatidylinositol-anchored proteins, aminopeptidase (APN) and alkaline phosphatase (ALP), have been shown to bind Cry1Ab, although their role in toxicity remains to be determined. Detection of Cry1Ab binding proteins by ligand blot assay revealed that ALP is preferentially expressed earlier during insect development, because it was found in the first larval instars, whereas APN is induced later after the third larval instar. The binding of Cry1Ab oligomer to pure preparations of APN and ALP showed that this toxin structure interacts with both receptors with high affinity (apparent K(d) = 0.6 nM), whereas the monomer showed weaker binding (apparent K(d) = 101.6 and 267.3 nM for APN and ALP, respectively). Several Cry1Ab nontoxic mutants located in the exposed loop 2 of domain II or in beta-16 of domain III were affected in binding to APN and ALP, depending on their oligomeric state. In particular monomers of the nontoxic domain III, the L511A mutant did not bind ALP but retained APN binding, suggesting that initial interaction with ALP is critical for toxicity. Our data suggest that APN and ALP fulfill two roles. First APN and ALP are initial receptors promoting the localization of toxin monomers in the midgut microvilli before interaction with cadherin. Then APN and ALP function as secondary receptors mediating oligomer insertion into the membrane. However, the expression pattern of these receptors and the phenotype of L511A mutant suggest that ALP may have a predominant role in toxin action because Cry toxins are highly effective against the neonate larvae that is the target for pest control programs.

Employing phage display to study the mode of action of Bacillus thuringiensis Cry toxins

Phage display is an in vitro method for selecting polypeptides with desired properties from a large collection of variants. The insecticidal Cry toxins produced by Bacillus thuringiensis are highly specific to different insects. Various proteins such as cadherin, aminopeptidase-N (APN) and alkaline phosphatase (ALP) have been characterized as potential Cry-receptors. We used phage display to characterize the Cry toxin-receptor interaction(s). By employing phage-libraries that display single-chain antibodies (scFv) from humans or from immunized rabbits with Cry1Ab toxin or random 12-residues peptides, we have identified the epitopes that mediate binding of lepidopteran Cry1Ab toxin with cadherin and APN receptors from Manduca sexta and the interaction of dipteran Cry11Aa toxin with the ALP receptor from Aedes aegypti. Finally we displayed in phages the Cry1Ac toxin and discuss the potential for selecting Cry variants with improved toxicity or different specificity.

Specific Epitopes of Domains II and III of Bacillus thuringiensis Cry1Ab Toxin Involved in the Sequential Interaction with Cadherin and Aminopeptidase-N Receptors in Manduca sexta

The Bacillus thuringiensis Cry toxins are specific to different insects. In Manduca sexta cadherin (Bt-R1) and aminopeptidase-N (APN) proteins are recognized as Cry1A receptors. Previous work showed that Cry1Ab binds to Bt-R1 promoting the formation of a pre-pore oligomer that binds to APN leading to membrane insertion. In this work we characterized the binding epitopes involved in the sequential interaction of Cry1Ab with Bt-R1 and APN. A Cry1Ab immune M13 phage repertoire was constructed using antibody gene transcripts of bone marrow or spleen from a rabbit immunized with Cry1Ab. We identified antibodies that recognize domain II loop 3 (scFvL3-3) or beta16-beta22 (scFvM22) in domain III. Enzyme-linked immunosorbent assay and toxin overlay binding competition assays in the presence of scFvL3-3, scFvM22, or synthetic peptides showed that domain II loop 3 is an important epitope for interaction with Bt-R1 receptor, whereas domain III beta16 is involved in the interaction with APN. Both scFvL3-3 and scFvM22 lowered the toxicity of Cry1Ab to M. sexta larvae indicating that interaction with both receptors is important for in vivo toxicity. scFvL3-3 and anti-loop2 scFv (scFv73) promoted the formation of the pre-pore oligomer in contrast to scFvM22. In addition, scFvL3-3 and scFv73 preferentially recognized the monomeric toxin rather than the pre-pore suggesting a conformational change in domain II loops upon oligomerization. These results indicate for the first time that both receptor molecules participate in Cry1Ab toxin action in vivo: first the monomeric toxin binds to Bt-R1 through loops 2 and 3 of domain II promoting the formation of the pre-pore inducing some structural changes, then the pre-pore interacts with APN through beta-16 of domain III promoting membrane insertion and cell death.

Glucogenosis tipo III asociada a carcinoma hepatocelular

Type III glycogen storage disease is a hereditary disorder with autosomal recessive transmission. It is characterized by accumulation of abnormal glycogen in the liver and, in 80% of patients, in muscle. The liver can also show fibrosis and sometimes cirrhosis. Until 2000, 9 cases of cirrhosis had been published, 3 of which showed associated hepatocarcinoma. We present the case of a 31-year-old woman, diagnosed in childhood with type III glycogen storage disease, who 30 years after onset developed a hepatocellular carcinoma with portal thrombosis in the context of advanced cirrhosis. This is the first case to be reported in the Spanish literature of type III glycogen storage disease associated with hepatocellular carcinoma.